feat(api): BAC-11 Websocket - Return to Lobby (#94)

Reviewed-on: #94
Co-authored-by: Janis <janis.e.20@gmx.de>
Co-committed-by: Janis <janis.e.20@gmx.de>

knockoutwhistweb/app/model/sessions/UserSession.scala

@@ -73,6 +73,8 @@ class UserSession(val user: User, val host: Boolean, val gameLobby: GameLobby) e
             case None =>
               println("Player ID not found or is not a valid UUID.")
           }
+        case "ReturnToLobby" =>
+          gameLobby.returnToLobby(this)
       }
     }
     lock.unlock()