Allow apng

[Yuripetusko]

Is your feature request related to a problem? Please describe.
Make sure that file upload dropzone allows apng images (animated pngs) if it isn't already

Describe the solution you'd like
Check if new mimetype needs to be added

Describe alternatives you've considered

Additional context

[redrocket94]

I succeeded in uploading an apng with no issues, it even played the animation in the dropdown area zone - curious to know if allowing apng should prohibit any "regular" png uploads like you currently have with other filetypes?

[Yuripetusko]

I think this is fine to allow a mixed of both png and apng in the same catalog, we just might have to adjust Singular code to handle apngs when rendering all parts, but this is a job for later I guess

[Yuripetusko]

So basically no changes needed for apng support? Dropbox allows it even though we specify particular mime types and file extensions?