Transition to packaging & configuration using pyproject.toml

[Dev-iL]

Transition to the more modern pyproject.toml from setup.cfg, requirements-*.txt etc.

Changes

Combined multiple files into one + added some placeholder for ruff & mypy.

How I tested this

python -m build --wheel

Notes

Addresses #10

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[skrawcz]

This fixes #10

[skrawcz]

thanks @Dev-iL !