…-found include dir, and look in default app-install OpenSCAD `libraries` directories as well as per-user libraries dirs

pyproject.toml:
Since poetry is used, switch to the build-system setup as documented
upstream (https://python-poetry.org/docs/pyproject#poetry-and-pep-517).

pyproject.toml:
Pkg_resources is used in solid/solidpython.py, hence this project
depends on setuptools until the use of pkg_resources is replaced with
something else.

… last rail points were the same had some ugly joins whether or not `connect_ends` was set. If first and last points are identical (within sqrt(EPSILON) of each other), assume we want to connect ends, and remove the duplicate rail point.

Switch to correct dependencies

- Removed pkg_resources, setuptools dependencies
- Updated pyproject.toml for use with `uv`
- Ruff formatting throughout
- Added Github CI to replace circleci-based testing

- Removed pkg_resources, setuptools dependencies
- Updated pyproject.toml for use with uv
- Ruff formatting throughout
- Added Github CI to replace circleci-based testing

…esources

Feature/correct pkg resources - update to drag us screaming into the 2020s