Upgrade to pyproject, bump pyupgrade

[asears]

This PR uplifts the project a bit. ++ @carltongibson

• Upgrade to pyproject.toml from setup.cfg and tox.ini
• Add pytest-cov test coverage settings
• bump pyupgrade version
• Add workflow dispatch to allow for tests workflow to be called on demand
• Add permissions to test workflow as per good security practice
• Comment the gitignore, add coverage exclusions
• Added some testing dependencies
• Added some project URLs

This PR will need a test by someone familiar with the release process and review of the settings for pypi release.

Some further improvements could be made:

• Add black, flake8, pytest, coverage, security scans to a build pipeline for inline visibility on pr/comments on prs.
• Some flake8 & ruff warnings to adjust/address
• One file needs format in the repo according to latest black.
• If some contributors are testing builds with uv, requires an extra couple lines added to pyproject to allow a wheel build.
• ruff could be added for future to replace need for isort, black, flake8, flake8-bugbear and autofix issues