Add RegisterOutgoingProcessor for Dart WS

[batchu5]

The Python websocket client has RegisterOutgoingProcessor, which is used to register middleware functions for Outgoing messages, but it is missing in the Dart client. How about we add this to the Dart WebSocket also?

[batchu5]

@Adi-204 please take a look at this issue!

[Adi-204]

@batchu5 you can work on issue or if you are not interest please do update issue description and add it is open for contribution.

[batchu5]

yep, I'm interested, will raise a PR soon.