Show a different icon for participants that you've muted

As a non-intrusive way to help you remember when you've locally muted a participant (so you're less likely to be confused about not hearing their audio), we can show a different icon on the tile.

public/locales/en-GB/app.json

@@ -192,6 +192,7 @@
     "collapse": "Collapse",
     "expand": "Expand",
     "mute_for_me": "Mute for me",
+    "muted_for_me": "Muted for me",
     "volume": "Volume"
   }
 }