Clean up, improve documentation, and prep for release #209

	name: unit tests

	on:
	push:
	branches:
	- "**"
	paths:
	- 'undate/**'
	- 'tests/**'
	pull_request:

	env:
	# python version used to calculate and submit code coverage
	COV_PYTHON_VERSION: "3.12"

	jobs:
	python-unit:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	python: ["3.9", "3.10", "3.11", "3.12", "3.13"]
	defaults:
	run:
	working-directory: .

	steps:
	- uses: actions/checkout@v3
	- name: Set up Python ${{ matrix.python-version }}
	uses: actions/setup-python@v4
	with:
	python-version: ${{ matrix.python }}
	cache: 'pip'
	cache-dependency-path: '**/pyproject.toml'
	- name: Install package with dependencies
	run: \|
	pip install -e ".[test]"
	if: steps.setup-python.outputs.cache-hit != 'true'

	# for all versions but the one we use for code coverage, run normally
	- name: Run unit tests normally
	run: pytest
	if: ${{ matrix.python != env.COV_PYTHON_VERSION }}

	# run code coverage in one version only
	- name: Run unit tests with code coverage reporting
	run: pytest --cov=undate
	if: ${{ matrix.python == env.COV_PYTHON_VERSION }}
	- name: Upload test coverage to Codecov
	uses: codecov/codecov-action@v3
	if: ${{ matrix.python == env.COV_PYTHON_VERSION }}

Provide feedback