Add AVIF

[JanisPlayer]

I'm currently making a change to Nextcloud that allows for the creation of JPEG previews from AVIF images. With this change, if the proposal is accepted, this app would also be up-to-date. But there's still one question that needs to be answered: How good is the browser support for AVIF? Can it be added to the well-supported formats without Edge's support, or not? The browser support for AVIF has greatly improved. Only Edge, Opera Mini, QQ Browser, KaiOS Browser, and of course IE don't support it anymore.

Closes #407

[skjnldsv]

83.35% support is a bit low to my taste :thinking:

[github-actions[bot]]

Hello there, Thank you so much for taking the time and effort to create a pull request to our Nextcloud project.

We hope that the reviewing process is going smooth and is helpful for you. We want to ensure your pull request is reviewed to your satisfaction. If you have a moment, our community management team would very much appreciate your feedback on your experience with this PR reviewing process.

Your feedback is valuable to us as we continuously strive to improve our community developer experience. Please take a moment to complete our short survey by clicking on the following link: https://cloud.nextcloud.com/apps/forms/s/i9Ago4EQRZ7TWxjfmeEpPkf6

Thank you for contributing to Nextcloud and we hope to hear from you soon!