Index: Add support for decoding JPEG XL images and playing PNG animations

[lastzero]

As a user with less common or new file formats like JPEG XL and APNG, I want PhotoPrism to recognize and index them so I can browse them along with my other pictures.

[lastzero]

Note that the JPEG XL decoder is not installed in our default Docker image. We may add it in a future release, e.g. when upgrading to Ubuntu 23.04.