Add `Progress` to `WhisperKit`

[finnvoor]

Currently there doesn't seem to be a way to get the current transcription progress to display. This adds a Progress to WhisperKit for easily displaying transcription progress in a ProgressView as seen in the modified WhisperAX.

The progress could probably be much more fine grained by updating in the decoder loop (and possibly factoring in model load time/anything else?), but this is a pretty good start I think.

[ZachNagengast]

This is cool, good idea! Although it looks a bit strange in streaming mode because the full audio length increases with every loop, can we just disable it for the streaming tab?

[finnvoor]

This is cool, good idea! Although it looks a bit strange in streaming mode because the full audio length increases with every loop, can we just disable it for the streaming tab?

Didn't notice that, should be fixed now ✅