HEIC avoidance

[edemaine]

iOS devices like to take pictures in HEIC, which isn't supported in any browser except Safari. Luckily, the browser sometimes converts to JPEG on web form uploads.

I'm hypothesizing that an <input accept="image/*,*/*"> attribute will encourage conversion. But it messes up desktop browsers (makes the default extension list just images). So maybe need to detect host system and add header accordingly?

Alternatively, perhaps we could detect HEIC on the client side, convert to JPEG on the client side (as the user is presumably using Safari, so the file can be supported), and upload that instead?