fix: clean up socketio dynamic namespaces

While serving many sites it's best to close down namespace when last
connection is closed.

refer https://github.com/socketio/socket.io/pull/4602

realtime/index.js

@@ -9,6 +9,7 @@ let io = new Server({
 		origin: true,
 		credentials: true,
 	},
+	cleanupEmptyChildNamespaces: true,
 });
 
 // Multitenancy implementation.