Type stubs for RPi.GPIO

RPi.GPIO is a Python module for controlling GPIO pins on Raspberry Pi. It is old and little maintained (they still use sourceforge.net!), but still useful today. It doesn't have type hints, so I added stubs for RPi.GPIO, now available on PyPI.

Incidentally I learned of distribution name normalisation. Package names can use ASCII letters, numbers, and ., - and _; but the normalised name is lower-cased with any run of punctuation characters replaced with a single dash, so rpi-gpio is the normal form for RPi.GPIO. pip the CLI tool and the PyPI web interface accept any form: pip install RPi.GPIO, or pip install rpi-gpio, or pip install rPi__GpIo will install the same package. pip-compile with use the normalized name when writing a constraints file.