Added /join description

webclient/settings/settings.html

@@ -81,6 +81,7 @@
             <ul>
                 <li>/nick &lt;display_name&gt;: change your display name</li>
                 <li>/me &lt;action&gt;: send the action you are doing. /me will be replaced by your display name</li>
+                <li>/join &lt;room_alias&gt;: join a room</li>
                 <li>/kick &lt;user_id&gt; [&lt;reason&gt;]: kick the user</li>
                 <li>/ban &lt;user_id&gt; [&lt;reason&gt;]: ban the user</li>
                 <li>/unban &lt;user_id&gt;: unban the user</li>