Add www.bazel.io --> bazel.build redirect

Extending js redirect to catch "www.bazel.io" in addition to "bazel.io"

Closes #2328.

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Reviewed-on: https://github.com/bazelbuild/bazel/pull/2328
PiperOrigin-RevId: 143457246
MOS_MIGRATED_REVID=143457246
diff --git a/site/_includes/head.html b/site/_includes/head.html
index 82b2254..5dfdb9f 100644
--- a/site/_includes/head.html
+++ b/site/_includes/head.html
@@ -6,7 +6,7 @@
 
     <script>
       var current_url = window.location.href;
-      var bad_url = new RegExp("^https?://(bazelbuild.github.io/bazel|bazel.io)/");
+      var bad_url = new RegExp("^https?://(bazelbuild.github.io/bazel|(www\.)?bazel.io)/");
       if (bad_url.test(current_url)) {
         window.location.replace(current_url.replace(bad_url, "https://bazel.build/"));
       }