Make demos work

[dannystaple]

Getting the demonstration code to run.
Tested on a real arm from a Raspberry Pi 5. With Bookworm, PyUsb 1.3.1.

• demos/key_ctrl.py has being pg_key_ctrl.py - and supports multiple keys at once.
• demos/sh_key_control.py - Designed for console key control and testing - great for just testing an arm
• demos/simple.py - simplest thing that does anything