add contributing readme

CONTRIBUTING.md

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+# Contributing
+
+We want to make contributing to this project as easy and transparent as possible.
+
+## Issues
+
+Please ensure your description is clear and has sufficient instructions to be able to reproduce the issue. The recommended issue format is:
+
+---
+
+#### To Reproduce
+
+`How to reproduce the issue.`
+
+#### Expected behavior
+
+`Expected output.`
+
+#### Environment
+
+`Your environment.`
+
+---
+
+## Developer environment
+
+Test project:
+
+```bash
+pytest .
+```
+
+Lint project:
+Linting is required for PRs. Lint via ruff or use the provided pre commit hooks.
+
+### Precommit hooks
+
+Hooks can be installed from .pre-commit-config.yaml. For example:
+
+1. `$ pip install pre-commit`
+2. `$ pre-commit install`
+
+## Pull Requests
+
+We actively welcome your pull requests.
+
+1. Fork the repo and create your branch from `main`.
+2. If you've changed APIs, update the documentation.
+3. Ensure the test suite passes (`pytest`). These are also required for PRs.
+4. Make sure your code lints (`ruff`). This is also required for PRs.
+
+## Coding Style
+
+We use
+[![Code style: ruff](https://github.com/astral-sh/ruff)](https://github.com/astral-sh/ruff)