message: Add pubsubhubbub feed information to template
diff: <subtitle>Recent Rust crates</subtitle>
  <link href="https://docs.rs/releases/feed" rel="self" />
  <link href="https://docs.rs/" />
  +<link href="https://pubsubhubbub.appspot.com" rel="hub" />
  +<link href="https://pubsubhubbub.superfeedr.com" rel="hub" />
  <id>urn:docs-rs:{{cratesfyi_version_safe}}</id>
  <updated>{{content[0].release_time_rfc3339}}</updated>
  {{#each content}}
  