Format for all previews AVIF

[GVLLIFESTYLE]

Please save and store all previews in AVIF format for faster loading time if possible ;)
best regards

[aentwist]

Potential duplicate of #13552

[aentwist]

Let's use this for adding AVIF support. The other issue covers allowing for the specification of preview format. So if both get done, we've got AVIF previews.

Note that PHP GD does not have AVIF. This will be coming from Imagick I guess (which does support it, read and write).

PHP should update their GD documentation.. imageavif

See also php/doc-en#1380

[aentwist]

Turns out it was pretty easy. Here are some notes from my adventures, which mostly involve build issues.

At this time using AVIF is not trivial due to system dependencies. TLDR - compile a current version of libaom for use on Debian bullseye. docker-php-extension-installer does this for you. The package manager's version should work in bookworm.

juliushaertl/nextcloud-docker-dev#182