content/static: add empty alt text for decorative icons

The empty alt text indicates to assistive technologies
that the image is decorative and can be ignored.

Change-Id: Ia48bdfe613c25bc178f2c0c1f6c6969340f9eb0d
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/260726
Trust: Jamal Carvalho <jamal@golang.org>
Run-TryBot: Jamal Carvalho <jamal@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>
diff --git a/content/static/html/helpers/_unit_directories.tmpl b/content/static/html/helpers/_unit_directories.tmpl
index f14825b..ca86375 100644
--- a/content/static/html/helpers/_unit_directories.tmpl
+++ b/content/static/html/helpers/_unit_directories.tmpl
@@ -7,7 +7,7 @@
 {{define "unit_directories"}}
   <div class="UnitDirectories" id="section-directories">
     <h2 class="UnitDirectories-title">
-      <img height="25px" width="20px" src="/static/img/pkg-icon-folder_20x16.svg">Directories
+      <img height="25px" width="20px" src="/static/img/pkg-icon-folder_20x16.svg" alt="">Directories
     </h2>
     {{if (or .Subdirectories .NestedModules) }}
       <table class="UnitDirectories-table">
diff --git a/content/static/html/helpers/_unit_doc.tmpl b/content/static/html/helpers/_unit_doc.tmpl
index 4839015..2b015d5 100644
--- a/content/static/html/helpers/_unit_doc.tmpl
+++ b/content/static/html/helpers/_unit_doc.tmpl
@@ -7,7 +7,7 @@
 {{define "unit_doc"}}
   <div class="UnitDoc" id="section-documentation">
     <h2 class="UnitDoc-title">
-      <img height="25px" width="20px" src="/static/img/pkg-icon-doc_20x12.svg">Documentation
+      <img height="25px" width="20px" src="/static/img/pkg-icon-doc_20x12.svg" alt="">Documentation
     </h2>
     <div class="Documentation js-documentation">
       {{if .DocBody.String}}
diff --git a/content/static/html/helpers/_unit_files.tmpl b/content/static/html/helpers/_unit_files.tmpl
index e155579..2f7626e 100644
--- a/content/static/html/helpers/_unit_files.tmpl
+++ b/content/static/html/helpers/_unit_files.tmpl
@@ -7,7 +7,7 @@
 {{define "unit_files"}}
   <div class="UnitFiles" id="section-sourcefiles">
     <h2 class="UnitFiles-title">
-      <img height="16px" width="12px" src="/static/img/pkg-icon-file_16x12.svg">Source Files
+      <img height="16px" width="12px" src="/static/img/pkg-icon-file_16x12.svg" alt="">Source Files
     </h2>
     <div>
       <ul class="UnitFiles-fileList">
diff --git a/content/static/html/helpers/_unit_fixed_header.tmpl b/content/static/html/helpers/_unit_fixed_header.tmpl
index 80c8908..4fa7adf 100644
--- a/content/static/html/helpers/_unit_fixed_header.tmpl
+++ b/content/static/html/helpers/_unit_fixed_header.tmpl
@@ -34,7 +34,7 @@
         {{if (eq .SelectedTab.Name "")}}
           <div class="UnitHeaderFixed-detail">
             <span class="UnitHeaderFixed-detailItem UnitHeaderFixed-detailItem--md">
-              <img height="16px" width="16px" src="/static/img/pkg-icon-arrowBranch_16x16.svg">
+              <img height="16px" width="16px" src="/static/img/pkg-icon-arrowBranch_16x16.svg" alt="">
               <a href="?tab=versions" tabindex="-1">Version {{.DisplayVersion}}</a>
               <!-- Do not reformat the data attributes of the following div: the server uses a regexp to extract them. -->
               <div class="DetailsHeader-badge $$GODISCOVERY_LATESTMINORCLASS$$"
@@ -44,11 +44,11 @@
               </div>
             </span>
             <span class="UnitHeaderFixed-detailItem UnitHeaderFixed-detailItem--md">
-              <img height="16px" width="16px" src="/static/img/pkg-icon-circularArrows_16x16.svg">
+              <img height="16px" width="16px" src="/static/img/pkg-icon-circularArrows_16x16.svg" alt="">
               {{.LastCommitTime}}
             </span>
             <span class="UnitHeaderFixed-detailItem UnitHeaderFixed-detailItem--md">
-              <img height="16px" width="16px" src="/static/img/pkg-icon-scale_16x16.svg">
+              <img height="16px" width="16px" src="/static/img/pkg-icon-scale_16x16.svg" alt="">
               {{range $i, $e := .Licenses}}
                 {{if $i}}, {{end}}
                 <a href="{{$.URLPath}}?tab=licenses#{{.Anchor}}" tabindex="-1">{{$e.Type}}</a>
@@ -61,13 +61,13 @@
             </span>
             {{if .Unit.IsPackage}}
               <span class="UnitHeaderFixed-detailItem UnitHeaderFixed-detailItem--lg">
-                <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg">
+                <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg" alt="">
                 <a href="{{$.URLPath}}?tab=imports" tabindex="-1">
                   {{len .Unit.Imports}} <span>Imports</span>
                 </a>
               </span>
               <span class="UnitHeaderFixed-detailItem UnitHeaderFixed-detailItem--lg">
-                <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg">
+                <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg" alt="">
                 <a href="{{$.URLPath}}?tab=importedby" tabindex="-1">
                   {{.ImportedByCount}} <span>Imported by</span>
                 </a>
@@ -94,7 +94,7 @@
           </div>
         {{else}}
           <a class="UnitFixedHeader-backLink" href="?">
-            <img height="16px" width="16px" src="/static/img/pkg-icon-arrowLeft_16x16.svg"> Go to main page
+            <img height="16px" width="16px" src="/static/img/pkg-icon-arrowLeft_16x16.svg" alt=""> Go to main page
           </a>
         {{end}}
       </div>
diff --git a/content/static/html/helpers/_unit_header.tmpl b/content/static/html/helpers/_unit_header.tmpl
index 88268a4..95da358 100644
--- a/content/static/html/helpers/_unit_header.tmpl
+++ b/content/static/html/helpers/_unit_header.tmpl
@@ -49,7 +49,7 @@
         {{end}}
       </div>
       <div class="UnitHeader-versionBanner $$GODISCOVERY_LATESTMAJORCLASS$$">
-        <img height="19px" width="16px" class="UnitHeader-detailIcon" src="/static/img/pkg-icon-info_19x16.svg">
+        <img height="19px" width="16px" class="UnitHeader-detailIcon" src="/static/img/pkg-icon-info_19x16.svg" alt="">
         <span>
           The latest major version is <a href="/$$GODISCOVERY_LATESTMAJORVERSIONURL$$">$$GODISCOVERY_LATESTMAJORVERSION$$</a>.
         </span>
@@ -58,7 +58,7 @@
       {{if (eq .SelectedTab.Name "")}}
         <div class="UnitHeader-detail">
           <span class="UnitHeader-detailItem">
-            <img class="UnitHeader-detailItemLarge" height="16px" width="16px" src="/static/img/pkg-icon-arrowBranch_16x16.svg">
+            <img class="UnitHeader-detailItemLarge" height="16px" width="16px" src="/static/img/pkg-icon-arrowBranch_16x16.svg" alt="">
             <a href="?tab=versions">Version {{.DisplayVersion}}</a>
             <!-- Do not reformat the data attributes of the following div: the server uses a regexp to extract them. -->
             <div class="DetailsHeader-badge $$GODISCOVERY_LATESTMINORCLASS$$"
@@ -68,11 +68,11 @@
             </div>
           </span>
           <span class="UnitHeader-detailItem">
-            <img height="16px" width="16px" src="/static/img/pkg-icon-circularArrows_16x16.svg">
+            <img height="16px" width="16px" src="/static/img/pkg-icon-circularArrows_16x16.svg" alt="">
             {{.LastCommitTime}}
           </span>
           <span class="UnitHeader-detailItem">
-            <img height="16px" width="16px" src="/static/img/pkg-icon-scale_16x16.svg">
+            <img height="16px" width="16px" src="/static/img/pkg-icon-scale_16x16.svg" alt="">
             {{if .Licenses}}
               <a href="{{$.URLPath}}?tab=licenses">
                 {{range $i, $e := .Licenses}}
@@ -86,13 +86,13 @@
           </span>
           {{if .Unit.IsPackage}}
             <span class="UnitHeader-detailItem">
-              <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg">
+              <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg" alt="">
               <a href="{{$.URLPath}}?tab=imports">
                 {{len .Unit.Imports}} <span>Imports</span>
               </a>
             </span>
             <span class="UnitHeader-detailItem">
-              <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg">
+              <img height="16px" width="16px" src="/static/img/pkg-icon-boxClosed_16x16.svg" alt="">
               <a href="{{$.URLPath}}?tab=importedby">
                 {{.ImportedByCount}} <span>Imported by</span>
               </a>
@@ -105,7 +105,7 @@
             data-version="{{.LinkVersion}}" data-mpath="{{.Unit.ModulePath}}" data-ppath="{{.Unit.Path}}" data-pagetype="{{.PageType}}">
         </div>
         <a class="UnitHeader-backLink" href="?">
-          <img height="16px" width="16px" src="/static/img/pkg-icon-arrowLeft_16x16.svg"> Go to main page
+          <img height="16px" width="16px" src="/static/img/pkg-icon-arrowLeft_16x16.svg" alt=""> Go to main page
         </a>
       {{end}}
     </div>
diff --git a/content/static/html/helpers/_unit_readme.tmpl b/content/static/html/helpers/_unit_readme.tmpl
index 0044555..37a87ec 100644
--- a/content/static/html/helpers/_unit_readme.tmpl
+++ b/content/static/html/helpers/_unit_readme.tmpl
@@ -7,7 +7,7 @@
 {{define "unit_readme"}}
   <div class="UnitReadme {{if .ExpandReadme}}UnitReadme--expanded{{end}} js-readme" id="section-readme">
     <h2 class="UnitReadme-title">
-      <img height="25px" width="20px" src="/static/img/pkg-icon-readme_20x16.svg">README
+      <img height="25px" width="20px" src="/static/img/pkg-icon-readme_20x16.svg" alt="">README
     </h2>
     {{if .Readme.String }}
       <div class="UnitReadme-content">