feat: Ability to get connection protocol

[Gold872]

Description

When connecting to a web socket server, you're able to pass a list of protocols your client will support. During the handshake between the client and server, the server will send back which protocol is being used. In some applications, it might be necessary for the client to know which protocol the server sent back. Right now there isn't a way to tell which protocol the server sent back, which wouldn't allow this API to be used for these types of applications. Having a way to access the protocol would be very useful in this case.

Requirements

• Some way of exposing the protocol through the WebSocket API