In Briar GTK [I shipped a `metainfo.xml` file](https://code.briarproject.org/briar/briar-gtk/-/blob/0.1.0-beta3/briar-gtk/data/app.briar.gtk.metainfo.xml.in) that is used by, e.g., GNOME Software to render a beautiful store entry with descriptions and screenshots (all translatable!). I have no idea how to ship this file with Compose, nor how we would generate the version including all translations. At Briar GTK [the build system Meson was doing this](https://code.briarproject.org/briar/briar-gtk/-/blob/0.1.0-beta3/briar-gtk/data/meson.build#L21) for us, therefore it has the appendix `.in`.