Feature Request: basic HDMI-CEC support.

Pulse-Eight sells a USB HDMI CEC adapter. It is the same one used in the raspberry pi as they provide the module for it. The adapter is cheap and can be used to do things like switch the TV input.

The following library includes a very simple to use command line client: https://github.com/Pulse-Eight/libcec. I believe an arch package exists for it.

I think it would greatly enhance the console experience if a command to turn the input active during bootup and a command to disable the input during shutdown was implemented. Additionally, turning the input off for suspend when pressing the power button and turning it on in resume would be desirable. This is similar to how Xbox implements their CEC so that you can turn a controller on and it wakes the console and turns the TV on. Waking the system with a USB Xbox wireless adapter already works, so cec-client is the only missing piece.

Turning the display off and on should be as simple as a systemd service that calls `echo as | cec-client -s` to turn it on and `echo standby 0 | cec-client -s` to turn it off during boot and shutdown respectively. If no CEC dongle is available this just won't do anything and is safe.

Start by reading the libcec project and the cec-client commands shown in the issue. Then inspect how ChimeraOS handles boot, shutdown, suspend, and resume system services. Done means the HDMI input is activated and put in standby at the requested lifecycle points, while systems without a CEC dongle remain unaffected.

Written by the indexing model from the issue text.