feat: toggle looping with soundfile mixer

[jamsea]

This allows a user to toggle looping audio when creating the mixer or dynamically with a control frame like this:

await task.queue_frame(MixerUpdateSettingsFrame({"sound": "ding", "loop": False}))

This allows users to trigger sound effects that aren't meant to be looped, e.g. a "ding" when a participant joins a call.

Music and Sound Effects Demo 🎵 - Watch Video

[aconchillo]

Just made a coupld of comments, but looks good! Thank you! 🙏