[Feature] add socket.io support for websocket-plugin

[xmlking]

As for I know, most of websocket backend implementations are based on Socket.io
it would be help full to support Socket.io transport for websocket-plugin

I have basic implementation here:
https://github.com/xmlking/ngx-starter-kit/tree/master/libs/socketio-plugin

wonder if @ngxs team interested to offer official support for Socket.io?

[splincode]

we can't supported socket.io by default