Add correct Appstream metadata
This is used by downstream packages and also by flathub to show the changelog for the latest flatpak version.
See: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html
This is used by downstream packages and also by flathub to show the changelog for the latest flatpak version.
See: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html