Support heic/heif attachments as photos

[julien-nc]

This small change is actually enough to support HEIC/HEIF files as image attachments.

This requires to have ImageMagic and the php-imagick module installed and the relevant preview providers enabled.
To enable the providers, one would need to have that in config.php:

'enabledPreviewProviders' =>
  array (
        1 => 'OC\\Preview\\HEIF',
        2 => 'OC\\Preview\\HEIC',
  ),

If the providers are not enabled, heic/heif files are considered as media attachment.

[mejo-]

Wouldn't the mimetypes also need to be added to src/helpers/mime.js?

[julien-nc]

Wouldn't the mimetypes also need to be added to src/helpers/mime.js?

Thanks for the fast review.
Actually no because we don't really display heic/heif files but jpeg previews of'em.

[mejo-]

Ah, makes sense. Thanks for the explanation 👍