* Add Whisper::VAD::Context
* Add test for Whisper::VAD::Context
* Add Whisper::VAD::Segment
* Add Whisper::VAD::Segments
* Add Whisper::VAD::Context#detect
* Define Whisper::VAD::Segments#each
* Define Whisper::VAD::Segment#start_time and #end_time
* Define Whisper::VAD::Segment#deconstruct_keys
* Add tests for Whisper::VAD family
* Add signatures for VAD family
* Add document on VAD in README
* Define Whisper::VAD::Segments#length
* Add test for Whisper::VAD::Segments#length
* Add signature of Segments#length
* Make vad_segments responsible to initialize VAD::Segments
* Remove meaningless argument check
* Check NULL of segments member
* Add tests for Whisper::VAD::Segments
* Initialize Whisper::VAD::Segment on .allocate
* Add tests for Whisper::VAD::Segment
* Check NULL of context member
* Add test for Whisper::VAD::Context.allocate
