[proposal] Can we provide WebSocket interfaces for customizing?

Hello, @kataras. the neffos.js works very well. but the coupling is too high. I want to change WebSocket. If there is an interface, I can implement it myself.

```js
interface EventCallback {
(evt: Event)
}

interface MsgCallback {
(evt: MessageEvent)
}

interface WebSocket {
Send(dat: string | ArrayBuffer);
Close();

OnMessage(cb: MsgCallback);
OnOpen(cb: EventCallback);
OnError(cb: EventCallback);
OnClose(cb: EventCallback);
}

// WS provided by the runtime
let ws = new WS;

let adapter: WebSocket = {
Send(dat) {
// logger
// ...
ws.send(dat)
},
Close(): void {
// ...
ws.close()
},
OnMessage(cb) {
// ...
ws.onMessage(cb);
},
OnOpen(cb) {
// ...
ws.onOpen(cb);
},
OnError(cb) {
// ...
ws.onErro(cb);
},
OnClose(cb) {
// ...
ws.onClose(cb);
}
};

neffos.SetWebsocketAdapter(adapter);
```

Start by tracing the existing WebSocket coupling in the library and reviewing the proposed WebSocket and SetWebsocketAdapter entry points. Define the adapter boundary and verify browser and Node.js behavior; done means consumers can provide a replacement implementation without changing neffos.js behavior.

Written by the indexing model from the issue text.