Add technical documentation for the package

- use sphinx to document the developed package
- create a nox session "docs" that builds the docs
- include a skeleton in the docs/ folder
  + how to install the package
  + how to use nox
  + license

src/urban_meal_delivery/__init__.py

@@ -13,9 +13,11 @@ try:
     _pkg_info = _metadata.metadata(__name__)
 
 except _metadata.PackageNotFoundError:  # pragma: no cover
+    __author__ = 'unknown'
     __pkg_name__ = 'unknown'
     __version__ = 'unknown'
 
 else:
+    __author__ = _pkg_info['author']
     __pkg_name__ = _pkg_info['name']
     __version__ = _pkg_info['version']