Add speakerSwitch flag in a SessionConfig

[Arkhypov]

Description:
Current SessionConfig.java does not have flag to enable_speaker_switch in a web Socket call:

# WebSocket protocol
wss://api.rev.ai/speechtotext/v1/stream?access_token=<REVAI_ACCESS_TOKEN>&content_type=audio/x-raw;layout=interleaved;rate=16000;format=S16LE;channels=1&transcriber=machine_v2&enable_speaker_switch=true

code to be added in StreamingClient.java:

if (sessionConfig.getSpeakerSwitch != null) {
        urlBuilder.addQueryParameter("enable_speaker_switch", sessionConfig.getSpeakerSwitch);
      }

Speaker diarization is important for our project.
If you want to give me access to create branch and pr in your repo, I can prepare pr for you.