Set up code base for development

[frans-johansson]

The current state of the code base is quite basic, and while this is not in and of itself a problem, it should at least try to follow some good practices for Python software development.

Following from The Hitchhiker's Guide to Python, the following changes or additions are proposed:

• [x] Rename main.py to palletize.py
• [x] Add a requirements.txt or Pipfile to project root
• [x] Add a test_pylettize.py with rudimentary unit tests
• [x] Add a LICENSE with an appropriate license
• [x] Add a setup.py to enable package installation
• [x] Set up code formatting and static code analysis
• [x] Set up pre-commit hooks

Consequently, the following decisions should be made before taking on this issue:

• Should a requirements.txt or Pipfile be set up
• What testing framework should be used?
• What software license is the most appropriate

Some work left for future issues include:

• A more thorough test suite
• Documentation under some sort of docs directory (as per the aforementioned Hitchhiker's Guide)
• Setting up GitHub workflows for automated testing and other CI niceties
• Maybe utilizing tox to test multiple Python environments

[frans-johansson]

Adding a setup.py would also be covered by #4, although perhaps a better ambition for this issue is to simply create the bare minimum required for local installation (i.e. development mode)

[frans-johansson]

The license file was committed straight to main, bypassing the ongoing PR

[frans-johansson]

Increasing the scope of this issue slightly:

• Set up code formatting and static code analysis
• Set up tox to run the unit tests
• Set up pre-commit hooks

[frans-johansson]

Descoping setting up tox to test multiple environments for now