Add Configuration "allowExtensions" for WebSocketServerHandshaker #253
Description
same as (netty/netty#2953) when connect to netty-socketio with a custom client，set WebSocketServerHandshaker.allowExtensions to true it works.
{{ message }}
same as (netty/netty#2953) when connect to netty-socketio with a custom client，set WebSocketServerHandshaker.allowExtensions to true it works.