Update Web Speech API externs

[avelad]

https://webaudio.github.io/web-speech-api/ has some new features.

Eg:

 // recognition parameters
 attribute boolean processLocally;

 // methods to drive the speech interaction
 undefined start(MediaStreamTrack audioTrack);
 static Promise<AvailabilityStatus> available(SpeechRecognitionOptions options);
 static Promise<boolean> install(SpeechRecognitionOptions options);

Is it possible add it?

Thanks!