devapp: give release-blocker its own axis on chart

There are so few release-blockers compared to total issues,
so that line on the chart ends up being hard to see.

Give it its own axis on the right, and allow it to scale independently.

Change-Id: Id2cd417b88dca8ae23405b7484d40e34b11e2094
Reviewed-on: https://go-review.googlesource.com/c/build/+/175117
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/devapp/templates/release.tmpl b/devapp/templates/release.tmpl
index 3be5920..269785b 100644
--- a/devapp/templates/release.tmpl
+++ b/devapp/templates/release.tmpl
@@ -110,6 +110,7 @@
     datasets: [
       {
         label: `${data.milestone} total issues`,
+        yAxisID: 'total',
         data: data.entries.map(d => d.open),
         backgroundColor: 'transparent',
         borderColor: 'rgba(54, 162, 235, 0.8)',
@@ -117,6 +118,7 @@
       },
       {
         label: `${data.milestone} release blocking`,
+        yAxisID: 'release-blocking',
         data: data.entries.map(d => d.blockers),
         backgroundColor: 'rgba(0,0,0,0)',
         borderColor: 'rgba(255, 99, 132, 0.8)',
@@ -142,9 +144,18 @@
     scales: {
       yAxes: [
         {
+          id: 'total',
           ticks: {
             beginAtZero: true,
           },
+          position: 'left',
+        },
+        {
+          id: 'release-blocking',
+          ticks: {
+            beginAtZero: true,
+          },
+          position: 'right',
         },
       ],
     },