Draft: systemd: add Wants=xsettingsd.service
A while ago, I added a systemd unit file to upstream xsettingsd:
https://github.com/derat/xsettingsd/commit/db54639d4305e5ae4cb84cd16ff4d628cc772d35
The unit file is in Fedora and Arch. It is still missing in Debian/Ubuntu and SUSE, because they are not yet using cmake (instead of scons) to build xsettingsd.