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 🤔

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[jlHertel]

Hey folks,
Any chance we can see this merged?

Browser support is now reported as > 94% and it seems to be supported in all major browsers.

[JanisPlayer]

@jlHertel One could add support for displaying the original image, but I don't think that's a priority right now. I have already implemented and tested full support, but have not received any feedback from the main developers. In another pool request, they said that they actually intend to do it, but I think the version has already passed. Therefore, the view would only be possible with the original file without preview. A separate app would be possible, though. Something like this already existed for Row pictures. Otherwise, the developer of this app must decide whether to allow the display of the original image if the browser supports it. It would also be possible to quickly convert to JPEG if the browser doesn't support it, but I think that would be a bit much. The problem is that it only works in the file browser, not in your gallery, and you can only identify the image by its name. Therefore, a separate app with a gallery fork would be better, which then also creates previews. But yes, it would be a start if you could view the images in the browser without downloading. If support is added in this app. That would be the problem, because it is not supported everywhere, but only here.