Websocket support

[haorendashu]

Using package github.com/gorilla/websocket to server websocket connection.
When call upgrader.Upgrade(w, r, nil), it return an error:

2024/04/10 21:16:42 failed to upgrade websocket: websocket: response does not implement http.Hijacker

It seems that the response need to implement http.Hijacker interface.

[syumai]

This library is using JS API directly, so it's hard to provide http.Hijacker interface for Conn.
But WebSocket support can be implemented using Durable Object, so I want to try another approach (without providing http.Hijacker).
Thank you for submitting this issue!