Specify protocol when creating Websocket connection

[fabian-rehm]

Component your feature request relates to

• Signalling server
• Frontend library
• Frontend UI library
• Matchmaker
• SFU
• This repo

Problem your feature solves? Please describe.
The current implementation of the WebSocket connection in the Pixel Streaming library lacks the flexibility to specify a protocol when establishing a connection to the signaling server. This limitation can hinder compatibility with certain signaling servers that require subprotocols for proper communication.

Describe the solution you'd like
When creating a websocket with the library 'ws' you can first specify the URL and optional specify a protocol.

https://github.com/EpicGamesExt/PixelStreamingInfrastructure/blob/master/Common/src/Transport/WebSocketTransportNJS.ts#L46
https://github.com/EpicGamesExt/PixelStreamingInfrastructure/blob/UE5.4/Frontend/library/src/WebSockets/WebSocketController.ts#L40

At those 2 positions it would be possible to specify the protocol in the exact way we would need it.
this.webSocket = new WebSocket(connectionURL, protocol);

Best possible solution would be to have a settings parameter to specify this protocol when creating the PixelStream object.