polyfill generic message event

front/src/Api/Events/IframeEvent.ts

@@ -11,6 +11,10 @@ import { OpenTabEvent } from './OpenTabEvent';
 import { UserInputChatEvent } from './UserInputChatEvent';
 
 
+export interface TypedMessageEvent<T> extends MessageEvent {
+    data: T
+}
+
 export type IframeEventMap = {
     //getState: GameStateEvent,
     // updateTile: UpdateTileEvent