feat: add systemd service to power off bluetooth during sleep

[jrouleau]

Fixes devices not reconnecting after resuming from sleep.

See https://github.com/jrouleau/bluetooth-autoconnect/issues/13 and https://github.com/jrouleau/bluetooth-autoconnect/issues/22

systemd-sleep scripts are considered 'hacks' and should not be shipped in packages. Use a systemd service instead. See https://wiki.archlinux.org/title/Power_management/Suspend_and_hibernate#Sleep_hooks