Replaced missing url

pages/index.html

@@ -138,7 +138,7 @@ <h1>Quality hosting</h1>
           <div class="row">
             <div class="col-md-12 text-center wp4">
               <h1>Community driven</h1>
-              <p>wallabag is an open source project <a href="https://github.com/wallabag/wallabag">hosted on GitHub</a>, made possible by an outstanding community of dedicated developers and users. The wallabag community contributes and shares their knowledge and experiences on our <a href="https://github.com/wallabag/wallabag">GitHub repository</a>, <a href="https://doc.wallabag.org/">the official documentation</a> and our <a href="https://gitter.im/wallabag/wallabag">Gitter.im chat room</a>.</p>
+              <p>wallabag is an open source project <a href="https://github.com/wallabag/wallabag">hosted on GitHub</a>, made possible by an outstanding community of dedicated developers and users. The wallabag community contributes and shares their knowledge and experiences on our <a href="https://github.com/wallabag/wallabag">GitHub repository</a>, <a href="https://doc.wallabag.org/">the official documentation</a> and our <a href="https://matrix.to/#/#wallabag:matrix.org">Matrix chat room</a>.</p>
               <ul class="text-center community-list" style="list-style: none;">
                 <li style="display: inline-block;margin: 3rem 3rem 0;">
                   <a href="https://github.com/wallabag/wallabag">