Merge pull request #343 from shurcooL/add-linux-js-env-pair

doc: Add "linux", "js" GOOS-GOARCH env pair.

doc/builder.go

diff --git a/doc/builder.go b/doc/builder.go
index d0e658b..a2b6e14 100644
--- a/doc/builder.go
+++ b/doc/builder.go
@@ -456,6 +456,7 @@
 	{"linux", "amd64"},
 	{"darwin", "amd64"},
 	{"windows", "amd64"},
+	{"linux", "js"},
 }
 
 // SetDefaultGOOS sets given GOOS value as default one to use when building