show in the UI if a player is disconnected

public/buzzer.html

@@ -15,7 +15,7 @@
         placeholder="Please put your name here ..."
     /></label>
     <h2>All Players</h2>
-    <ul>
+    <ul class="players">
       <!-- players will be inserted here -->
     </ul>
   </div>
@@ -27,7 +27,7 @@
 </body>
 
 <template id="player">
-  <li data-cid="client ID">player name</li>
+  <li class="player" data-cid="client ID">player name</li>
 </template>
 
 <script type="module" src="./buzzer.js"></script>