Add CEC daemon script
Allows input using the TV remote on CEC supported devices. Adapted and modernized from https://invent.kde.org/plasma-bigscreen/bigscreen-debos-image-rpi4/-/blob/master/overlays/bigscreen/etc/skel/.config/autostart-scripts/cec-daemon.py
Tested on Wayland and libcec >= 6.0.x
Fixes #18 (closed).