Add RSS feed

Publish an RSS feed of the changes to the specs repository to make the
specs more discoverable.

Do not include the template in the toctree so it will not be included in
the RSS feed.

Use the doc build date to produce the copyright string instead of using
a hard-coded value.

Change-Id: Ib4f84efab8b3af3ddd47d38d63a91362612bd655
Merge "Add RSS feed"