Consider making client notification a stream

[kubinio123]

Instead or along side of the current API:

client.onServerNotification:
      case ServerNotification.Progress(params)       => println(s"progress: ${params.progress}")
      case ServerNotification.LoggingMessage(params) => println(s"log: ${params.data}")
      case _                                         => ()

I would like to have a method that returns Stream[ServerNotification] specific to client effect backend.

client.serverNotifications(): Stream[ServerNotification]