Merge 'Upgrade to Sphinx 3'

.gitlab-ci.yml

Documentation/bluetooth/ess.rst

Documentation/conf.py

Documentation/hawkmoth/README.rst

Documentation/hawkmoth/VERSION

Documentation/hawkmoth/__init__.py

Documentation/hawkmoth/__main__.py

Documentation/hawkmoth/parser.py

Documentation/hawkmoth/util/docstr.py

Documentation/hawkmoth/util/readthedocs.py

Documentation/pycardium/png.rst

docker/deploy-env/Dockerfile

epicardium/epicardium.h

epicardium/modules/stream.h

tools/code-style.sh