Change Matrix room URI

source/_nav.erb

@@ -10,7 +10,7 @@
        <a href="https://github.com/Plume-org/Plume">Source code</a>
     </li>
     <li>
-       <a href="https://riot.im/app/#/room/#plume:disroot.org">Chat room</a>
+       <a href="https://matrix.to/#/#plume-blog:matrix.org">Chat room</a>
     </li>
     <li>
        <a href="https://fediverse.blog/~/PlumeDev">Updates</a>