Appdata: update the appdata per the latest specs

Freedesktop specs: https://freedesktop.org/software/appstream/docs/chap-Quickstart.html

GNOME Software Kudos specs: https://gitlab.gnome.org/GNOME/gnome-software/blob/master/doc/kudos.md

The provides -> binary and the categories are extracted from the desktop file using appstream-compose. You can try that yourself :)