Add support for the JPEG XL file format

[vanillajonathan]

https://en.wikipedia.org/wiki/JPEG_XL
https://caniuse.com/jpegxl

[nekohayo]

The biggest potential I see for this application is to be able to shrink down the heavy weight of my big photo gallery/storage on my computer, as I'm always running out of disk space. Curtail supporting JPEG XL for batch transcoding would be a huge deal. It would be the most efficient image codec, and it would be an order of magnitude faster to encode than anything else.

Conversion from JPEG to JPEG XL can be without degradation, and can be backwards compatible, so it's really the best archival format.

JPEG XL can even replace PNG, because with lossless JXL you get an average of 30-40% filesize improvements compared to optimized PNG: https://www.reddit.com/r/jpegxl/comments/l9ta2u/how_does_lossless_jpegxl_compared_to_png/