sound: Enable users to use a custom alert sound
Following discussion in !2345 (closed) wrt adding back an alert sound that was previously in Gnome, @jimmac has suggested to enable users to select a custom alert sound.
@jimmac has designed a mockup in: Teams/Design/settings-mockups@51233c74
As shown in the design, the feature would have several aspects:
- Enable users to pick a file from the alert sound panel
- Enable users to select that picked sound or another, default sound
- Copy the file internally so that it still works after the file is deleted by the user