Add audio stop event

[LeXXik]

This is a feature request.

We can start playback of an audio slot with .play() method. However, we don't know when it has stopped playing. As we are using AudioScheduledSourceNode for the audio instance, we can also know when the audio stops either by user initiated stop or the natural stop when the buffer reaches the end. It would be useful to add an event that we could listen to know when the audio stopped.

https://developer.mozilla.org/en-US/docs/Web/API/AudioScheduledSourceNode/ended_event

[yaustar]

Possible event names:

ended
finished

If it's a looping effect, should we still fire the same event or something else like the tween.js which has loop event

[LeXXik]

An option is to align it with anim component events in terms of naming and types.