GIF Support in Imageviewer

[pilian]

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• [x] I have searched existing issues for duplicates
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Summary

The buildin imageviewer should also display animated GIF images

Motivation

Many collection of pictures contain JPG and also GIF images. The imageviewer of Cryptomator don't show GIF images. It is very unhandy to switch to the Android Viewer for GIF-Images every time a GIF occurs.

Display of all images inside Cryptomator is very recommended.

Considered Alternatives

No response

Anything else?

No response