message: Updated footer with two links
  Added links to backstage.spotify.com and Community Sessions.
diff: @@ -44,6 +44,10 @@ class Footer extends React.Component {
  <a href="https://github.com/backstage/backstage/blob/master/CONTRIBUTING.md">
  Contributing
  </a>
  + <a href="https://backstage.spotify.com">Adopting</a>
  + <a href="https://github.com/backstage/community">
  + Community Sessions
  + </a>
  <a href="https://mailchi.mp/spotify/backstage-community">
  Subscribe to our newsletter
  </a>
  