Change Gitter to Matrix

Author: ZeiP

_includes/custom/asides/community.html

@@ -3,10 +3,10 @@
   <h1>Community</h1>
 
   <ul>
-  <li><a href="https://gitter.im/TracksApp/tracks">Gitter chat</a></li>
   <li><a href="http://groups.google.com/group/TracksApp">Mailing list</a></li>
   <li><a href="https://github.com/TracksApp/tracks/wiki">Wiki</a></li>
   <li><a href="https://webchat.freenode.net/#Tracks">#Tracks</a> on <a href="https://freenode.net">Freenode IRC network</a></li>
+  <li><a href="https://matrix.to/#/#tracks:matrix.org">#Tracks on Matrix.org</a> (bridged to the IRC channel)</a></li>
   </ul>
 
 </section>

contribute/index.md

@@ -8,7 +8,7 @@ footer: false
 
 We gladly welcome all contributions! There are many ways you can help.
 If you need help to get started, check out the resources below and drop
-in on [Gitter](https://gitter.im/TracksApp/tracks) for a chat!
+in on [Matrix](https://matrix.to/#/#tracks:matrix.org) for a chat!
 
 * [Report a bug or a feature request](https://github.com/TracksApp/tracks/issues)
 * [Contribute code or localisations](https://github.com/TracksApp/tracks/blob/master/CONTRIBUTING.md)