Implement new cowbesite system on API

front/src/Api/Events/CloseCoWebsiteEvent.ts

@@ -0,0 +1,12 @@
+import * as tg from "generic-type-guard";
+
+export const isCloseCoWebsite = new tg.IsInterface()
+    .withProperties({
+        id: tg.isOptional(tg.isString)
+    })
+    .get();
+
+/**
+ * A message sent from the iFrame to the game to add a message in the chat.
+ */
+export type CloseCoWebsiteEvent = tg.GuardedType<typeof isCloseCoWebsite>;