Add JPEG XL lossless transcoding of JPG support

[o-l-a-v]

JPEG XL can losslessly transcode JPG with a claimed gain of around 20%. But then it's lossless and can be reverted.

About this particular feature:

• https://cloudinary.com/blog/legacy_and_transition_creating_a_new_universal_image_codec#legacy_friendly_jpeg_xl
• https://gist.github.com/cedrickchee/a5aa40e8e6e00e8e4c8dc7aae9a3718e

More info about JPEG XL:

• https://jpegxl.info/
• https://jpegxl.io/articles/faq
• https://caniuse.com/?search=jpg%20xl
  • Available behind a flag in Chromium based browsers (https://chromestatus.com/feature/5188299478007808) and Firefox nightlies (https://bugzilla.mozilla.org/show_bug.cgi?id=1539075), hopefully it will be on by default in near future.