[Copilot]

The repository lacked contributor guidance. Adds CONTRIBUTING.md covering the full contributor workflow.

What's included

• Issues – when to open one (bugs, features, and before starting larger changes/refactors)
• Pull Requests – PRs must be focused on one thing; larger scope requires a prior issue discussion
• Local setup – clone + pip install -e ".[testing]"
• Tests – python -m pytest tests
• Static analysis – python -m mypy -v (references .mypy.ini)
• Deployment – maintainers cut a GitHub Release; python-publish workflow handles the PyPI upload automatically

[Copilot]

Pull request overview

Adds contributor guidance to the repository by introducing a CONTRIBUTING.md that documents the expected workflow for issues, pull requests, local setup, testing, static analysis, and release publishing. The instructions align with the existing repo configuration (e.g., requires-python >=3.9, .mypy.ini, tests/, and the python-publish workflow).

Changes:

• Add a new CONTRIBUTING.md with guidance on when/how to open issues and submit focused PRs.
• Document local development setup using pip install -e ".[testing]".
• Document how to run tests (python -m pytest tests), mypy (python -m mypy -v), and how releases are published via GitHub Actions.

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