The source project of this merge request has been removed.
Enable thumbnails for AVIF images
AVIF image format is now supported by kimageformats
This change activates thumbnails in dolphin.
image/avif mimetype is declared in the system via shared-mime-info 2.0. On systems using older versions of shared-mime-info, there is chance that the mimetype was installed via some other packages (for example libheif).