FEATURE: Support converting HEIF images to JPEG (PR #10079)

This is an optional feature (default off) to convert HEIF images (like live photos from iOS devices, for example) to be converted to jpegs when uploaded. Browsers do not support rendering HEIFs at this time.

Requires allowing heic and/or heif in the authorized_extensions site setting.


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I wonder, can we do this on the client-side? How CPU-intensive is it? Any ideas?