iOS HEIC images don't work

[phette23]

Package version (if known): 2.2.1 and all prior

Describe the bug

Apple's iOS devices save HEIC images with misleading .jpg extensions which tricks previewer into thinking that it can preview them but (almost all) web browsers cannot render these images.

Steps to Reproduce

1. Create a record with all required fields
2. Attach a HEIC image with a .jpeg extension
3. Publish the record

Expected behavior

HEIC images should be skipped, treated like other image formats that are not previewed, such as WebP. Instead, previewer thinks it can use the simple_image previewer, but the image does not render in the img tag because browser rendering engines cannot display HEIC.

Screenshots (if applicable)

Additional context

I think the solution would involve using some kind of file type detection library (filetype, puremagic) which looks at the bytes of the image file to determine whether they can be previewed instead of relying upon their extension. This would have a bonus effect of fixing previews of files with misleading extensions (e.g. plain text file with .png extension).