Added VAD request capability to server

[aabmets]

@rotemdan Would you be open to accepting this PR, which adds VAD request serving capability to the server and detectVoiceActivity to the client class? I kinda need it for my project.

[aabmets]

Input type on line 376 is fixed in 97d3b1d

[rotemdan]

Thanks for the contribution. I originally wrote the WebSocket server for mostly TTS serving to a browser extensions. I actually use this server all the time for TTS (via an unpublished extension), but I haven't really made any work on it since it was originally written..

I know it doesn't make much sense to have the WebSocket-based client as part of the main, heavy package. It was actually written mostly for testing the server (I use custom code in the browser extension instead, not based on the Client code at all). Ideally it should be a separate, lightweight package. For that reason I didn't put this on a high priority for development. I don't consider it that usable at the current state.

I'll merge your code but it will require to refresh my memory on something I haven't touched for more than a year now, and didn't have much interest working on.