appdata: Improve the appdata file per the specs
freedesktop specs:https://freedesktop.org/software/appstream/docs/chap-Quickstart.html kudos documentation: https://gitlab.gnome.org/GNOME/gnome-software/blob/master/doc/kudos.md
freedesktop specs:https://freedesktop.org/software/appstream/docs/chap-Quickstart.html kudos documentation: https://gitlab.gnome.org/GNOME/gnome-software/blob/master/doc/kudos.md