Add documentation for pyagl to docs.automotivelinux.org

Please add documentation to the master branch. Thank you!

There is a placeholder here:

https://docs.automotivelinux.org/en/master/#5_Component_Documentation/7_pyagl/

Git sources are here:

git clone https://git.automotivelinux.org/AGL/documentation

Edit docs/5_Component_Documentation/7_pyagl.md
git add
git commit -s -m"...................."
git review -s
git review