_content: link to atom feed
_content: link to atom feed

Fixes golang/go#47795

Change-Id: I6a4561c8e49a9c799f34347e166cc4813f59c2fc
Reviewed-on: https://go-review.googlesource.com/c/website/+/364276
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Trust: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
Website-Publish: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website