* APNG loader: Import addon to take over APNG handling
* APNG loader: Transition code to using the AImgIO addon
* APNG loader: Can now open APNGs.
* AImgIO: Update to fix bugs
* APNG loader: HTML5
* APNG loader: gdformat/gdlint addon
* APNG loader: OpenSave formatting fix
* APNG Loader: Add ignore line to OpenSave because it's too big
* Fix GIFAnimationExporter bug caused by the switch to the addon
