Can't add extra headers like it is implemented on js or swift

[Kolyall]

Add possibility to add extraheaders to start connection like it is implemented on js or swift

[muhammadnasr]

👍

[darrachequesne]

This was implemented in version 2.0.0: socketio/engine.io-client-java@dfe65e3

Reference: https://socketio.github.io/socket.io-client-java/initialization.html#extraHeaders