feat: add pypi CD pushing

[randomicecube]

Goal: being able to publish to PyPi via CD

Currently:

• Loose skeleton for a CD workflow to push to PyPi via Github Action;
• pyproject.toml and setup.cfg, with the latter missing install_requires, which should only be written after confirming requirements.txt packages

Afterward, need to check whether the action is fully working rn (need a PyPi API key to be a repo secret as well)

BTW, as currently set up, the action should only publish to PyPi after a tag is released.

Closes #6