* Initial work on audio layers
* Load ogg audio files
* Fix playback position
* Support mp3 files
* Play audio at the appropriate position when the animation runs, and stop when the pause button is pressed
* Change audio cel textures for the cels where audio is playing
* Fix audio not playing at the appropriate position
* Don't play audio is layer is invisible
* Set the audio layer names to be the imported audio file names
* Import audio from videos
* Export videos with audio
Only works with mp3 for now
* Remove support for ogg audio files as they cannot be saved
At least until I find a way to save them. Wav files will be supported with Godot 4.4
* Fix adding/removing in-between frames breaking the visual indication of audio cels
* Minor code improvements
* Export audio in videos with custom delay
* Support frame delay
* Change the frame where the audio plays at
* Fix crashes when the audio layer has no track
* Remove unneeded cel properties for audio cels
* Pxo loading/saving
* Load audio files from the audio layer properties
* Change the audio driver to Dummy from the Preferences for performance reasons
* Clone audio layers, disable layer merge and FX buttons when an audio layer is selected
* Easily change the playback frame of an audio layer from the right click menu of cel buttons
* Update Translations.pot
* Some code improvements and documentation
* Stop audio from playing when looping, and the audio does not play at the first frame
* Update audio cel buttons when changing the audio of the layer
* Mute audio layer when hiding it mid-play
* Only plays the portion of the sound that corresponds to the specific frame so maybe we should do that as well
When the animation is not running. If it is running, play the sound properly.
* Some code changes to allow for potential negative frames placement for audio
This woud allow audio to be placed in negative frames, which essentially means that audio would start before the first frame. This is not yet supported, however, because I don't know how to make it work with FFMPEG.
Not the most performance-friendly solution, but it works. If users encounter performance issues in the future, we should rewrite this, as it does the same for loop two times.
