Mark this library as deprecated and give a better alternative in README

[japsu]

This library is no longer required on Node.js due to the fact that the socket.io-client library nowadays has built-in support for setting extra headers such as cookies:

const io = require('socket.io-client');

const cookie = 'connect.sid=xyz';
const socket = io(url, { path, extraHeaders: { cookie } });

This is documented in the underlying engine.io-client library:

https://github.com/socketio/engine.io-client#nodejs-with-extraheaders