Feat : add messages

game.events.ts

@@ -20,8 +20,16 @@ export class GameJoinEvent {
 
 export class GameLeaveEvent {
   type = 'leavegame';
-  gameId?: number;
   constructor(public player: PlayerResponseDTO) {
     this.player = new PlayerResponseDTO(player);
   }
 }
+
+export class GameMessageEvent {
+  type = 'message';
+  constructor(
+    public gameId: number,
+    public authorId: number,
+    public message: string,
+  ) {}
+}