Add improvements to the audio editor

The fact that FlipaClip even HAS an audio editor in the first place is awesome, but to make it even better, I’d love to have a way to make the volume of the audio vary without changing the whole audio layer’s volume. Maybe the audio editor could use keyframes to gradually increase/decrease the layer’s volume. Or at least, it could have some sort of fade in and/or fade out option. For now, if I want to do that, I’ll just put the animation into a separate editing program, but it would be a nice addition.