Description of requested feature:

Add AVIF Format

Reasons for adding feature:

AVIF is more compression efficient than older image formats, with file sizes that can be 50% smaller than JPEG and 20-30% smaller than WebP. AVIF uses advanced compression techniques, such as AV1's inter- and intra-frame coding, to reduce redundancy and compress images.

https://caniuse.com/avif

Extra information, such as Shutter version, operating system and ideas for how to implement:

Arch Linux