[feature request] APNG support

[lublak]

APNG is a file which contains several png data.
These can then also be zlib compressed.
https://wiki.mozilla.org/APNG_Specification

https://github.com/photopea/UPNG.js/blob/master/UPNG.js

[Pign]

Hi,

I'll be starting some work on that issue on Epikowa's fork as I need some APNG methods : https://github.com/epikowa/format

Obviously, I'll offer to merge upstream.