Enable permessage-deflate to have websocket compression

[Yasso9]

Describe the feature

Hi, first thanks to this very cool library and the integration with nitro and nuxt.

Is it possible to have Sec-WebSocket-Extensions: permessage-deflate when answering a client connection ? Currently it does not respond to enabling permessage-deflate when the client ask to like on this one :

I have Sec-WebSocket-Extensions: permessage-deflate on the request header but nothing on the response header.

Additional information

• Would you be willing to help implement this feature?

[Yasso9]

Is having this sufficient inside the defineWebSocketHandler object ?

upgrade(req) {
  return {
    headers: {
      "sec-websocket-extensions": "permessage-deflate",
    },
  };
},