Implement VAD functionality for WakeWordSatellite

[jhbruhn]

I copied over the VAD implementation to be used together with the WakeWordSatellite. I decided to implement it here instead of in wyoming-openwakeword (rhasspy/wyoming-openwakeword#16) for now. It does seem to work reasonably well and integrates fully with the standard VAD configuration options.

Wakeword detection gets a bit slower if this is used because it will have to run OWW on the whole VAD buffer, but that should also be the same in streaming mode. Perhaps there are better configuration options for the default case which I haven't found yet.

[jhbruhn]

On second thought, it might be more efficient to implement this in the OWW service, similar to the original OWW implementation. That enables to score the single audio chunks with a wakeword and VAD score simultaneously, which should alleviate the latency problem.

[synesthesiam]

Thank you for the effort, but this will be included as part of the wyoming-openwakeword system in a future release: rhasspy/wyoming-openwakeword#27

[jhbruhn]

No worries, this is the way to go as I've also found out :)