Controller types for WebSocket

Add types to controller.ts for handling websocket connections:

• The WebSocketResponse interface can be used to initiate a connection
• The WebSocketEvent type can be used by a webSocketEvent(event: WebSocketEvent) function in a controller to handle incoming messages and connections.
• The Request.webSocket constant can be used to check if this is an attempt to open a web socket connection in a get(req: Request) function.