Function startListening

Start listening for speech.

Begins audio capture from the microphone and starts recognition. The recognizer must be in the RecognizerState.ReadyToListen state (call prepareForListening first).

While listening:

• Partial results are delivered via the onPartialResult callback as speech is recognized.
• When VAD detects the end of speech, the final response is delivered via the onFinalResponse callback.