Automount sdcard and add it to bookmarks/locations in GTK file dialog
We can ship a systemd automount unit to to e.g. automount to
/sdcard writeable by user purism and add it to the gtk file choser locations (add least that used to be possible) so it becomes visible/usable in GTK all apps right way.
The upside over just using file-choser's mount is that we unount when not in use.