Also add a reference to the strings blog post.

Fixes #11045.

Change-Id: Ic0a8908cbd7b51a36d104849fa0e8abfd54de2b9
Reviewed-on: https://go-review.googlesource.com/10662Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>