Migrate packaging to a pyproject.toml file and add wheel deployment

[rndubs]

Closes #19 #17 .

Key Changes:

• Migrated from setup.py to pyproject.toml - Moved all package configuration to the modern pyproject.toml standard
• Switched to setuptools-scm versioning - Replaced versioneer with setuptools-scm for automatic version management from git tags
• Added wheel deployment - Updated PyPI GitHub Action to build and test both sdist and wheel distributions
• Bumped minimum Python version to 3.9 - Dropped support for Python 3.7/3.8
• Updated CI/CD workflows - Modified GitHub Actions to use Python 3.9+ and check for pyproject.toml changes
• updated MANIFEST.in - Exclusion of development files from source distributions to account for setuptools-scm adoption
• Updated pre-commit hooks - Upgraded dependency versions and fixed compatibility issues

Distribution

Checking contents of the sdist:

% tar -xzvf dist/cons-0.4.7.dev12+dirty.tar.gz
x cons-0.4.7.dev12+dirty/
x cons-0.4.7.dev12+dirty/LICENSE.txt
x cons-0.4.7.dev12+dirty/MANIFEST.in
x cons-0.4.7.dev12+dirty/PKG-INFO
x cons-0.4.7.dev12+dirty/README.md
x cons-0.4.7.dev12+dirty/cons/
x cons-0.4.7.dev12+dirty/cons/__init__.py
x cons-0.4.7.dev12+dirty/cons/core.py
x cons-0.4.7.dev12+dirty/cons/unify.py
x cons-0.4.7.dev12+dirty/cons.egg-info/
x cons-0.4.7.dev12+dirty/cons.egg-info/PKG-INFO
x cons-0.4.7.dev12+dirty/cons.egg-info/SOURCES.txt
x cons-0.4.7.dev12+dirty/cons.egg-info/dependency_links.txt
x cons-0.4.7.dev12+dirty/cons.egg-info/requires.txt
x cons-0.4.7.dev12+dirty/cons.egg-info/top_level.txt
x cons-0.4.7.dev12+dirty/pyproject.toml
x cons-0.4.7.dev12+dirty/setup.cfg

[rndubs]

@brandonwillard , this should be ready for a review.

[brandonwillard]

@rndubs, much appreciated!

[rndubs]

you're welcome! I think this now just needs a git tag for the version bump and for the pypi deployment action to kick off.