Add sound notification

[niboshi]

This PR adds a feature to play sound file on prompt completion.

2 new setting entries are added to configure audio files that are played on the following events:

• When execution of one prompt is completed
• When execution of all prompts are completed

I'm aware there are some custom nodes for sound notification, but

• I feel this is so essential that I would like to have it as a core feature for better usability.
• it would be better to make workflows agnostic to this feature.

[huchenlei]

Can you attach steps with screenshots how this feature should be used?

[niboshi]

Sure. It's very simple though.

1. Open settings and select audio file(s)
   

2. Run workflow(s)

[huchenlei]

How do I enable/disable the sound notification? User probably don't want to re-upload an audio file to re-enable it. We should also provide a default sound effect.

[niboshi]

As for enable/disable, how about adding a mute setting (and perhaps volume setting) to each of the two?

I thought this feature could be opt-in, so a default sound would not be needed.
What should it be if we need it?

[huchenlei]

As for enable/disable, how about adding a mute setting (and perhaps volume setting) to each of the two?

I thought this feature could be opt-in, so a default sound would not be needed. What should it be if we need it?

I think if no custom sound is provided, we can use the classic linux beep sound. This is to simplify setup for anyone who wants to enable this feature. Removing the finding a sound file online, download it, upload it to ComfyUI steps.

[niboshi]

OK. As we can't play the system beep sound from frontend, I'll try to find some license-free sound file online that we can add to the repository.