Audio 2.0 about abovevtt

[vlaminck]

After playing with this a bit, here are my thoughts for UX requirements. Most of these are already reflected in the body of this Issue.

Mixer

1. Pinned to the top of the audio panel, and always accessible regardless of scrolling the audio panel body [DONE]
2. Master Volume that controls local playback volume [DONE]
3. Play/Pause toggle for all active channels [DONE]
4. A button for clearing all active channels [DONE]
5. A button for saving the current mixer as a Stage

Individual Channels within the mixer

1. track name [DONE]
2. volume control [DONE]
3. playback duration progress for each channel
4. play/pause toggle for each channel
5. loop toggle for each channel
6. mute for each channel? (Probably not needed. Might make it too crowded)

Track Listing

1. Scrollable list of existing tracks [DONE]
2. Bulk import of tracks [DONE]
3. Add a track to the mixer [DONE]
4. Only allow a track to be in the mixer once (can probably just disable the button that adds it to the mixer, but might want some other UI to indicate that it's already there)
5. Add a single track
6. Delete a single track
7. Edit a single track

Stage Listing

1. Scrollable list of existing stages
2. Button to replace mixer with a given stage
3. Delete a stage
4. Edit a stage (This could just be: load into mixer, change what you want, save as stage)

[github-actions]

Included in 0.90-beta2

[github-actions]

Included in 0.90