Support conversion to/from APNG

[pigsflew]

Should be classified as an animation format (like GIF).

From: Any video, any other animation format. To: Any video, any other animation format.

It'd actually be really nice to create and edit input formats for ones that ffmpeg supports but aren't (yet) in FileConverter. This would include format key (e.g. apng; tiff; avif; aiff), extension (.apng; .tif, .tiff;.aif, .aiff) etc. This would also allow people to get by several of the extant open issues...

[pigsflew]

I just found #90 that seems to allow this, but given that that was merged into integration in 2019 and there hasn't been a release since 2017... is this abandonware?

[SysAdminDoc]

Looks like it has been abandoned. What a shame, such a great project.

[Tichau]

Hello, Can you send here a sample apng file. Thanks

[DearFox]

Hello, Can you send here a sample apng file. Thanks

https://d.furaffinity.net/art/dearfox/1587143591/1587143591.dearfox_b2d6eb0c.png