message: CI checks if the documentation builds without warnings
diff: @@ -38,6 +38,9 @@ pylint --rcfile=pylint.ini xain && echo "===> pylint says: well done <===" &&
  # type checks
  mypy --ignore-missing-imports xain && echo "===> mypy says: well done <===" &&
  +# documentation checks
  +sphinx-build -W -b html docs/ docs/_build/ && echo "===> sphinx-build says: well done <===" &&
  +
  # tests
  pytest -v && echo "===> pytest/unmarked says: well done <===" &&
  