Add a config object

- add the following file:
  + src/urban_meal_delivery/_config.py
- a config module is created holding two sets of configurations:
  + production => against the real database
  + testing => against a database with test data
- the module is "protected" (i.e., underscore) and imported at the
  top level via a proxy-like object `config` that detects in which of
  the two environments the package is being run

pyproject.toml

@@ -28,6 +28,7 @@ repository = "https://github.com/webartifex/urban-meal-delivery"
 python = "^3.8"
 
 click = "^7.1.2"
+python-dotenv = "^0.14.0"
 
 [tool.poetry.dev-dependencies]
 # Task Runners