docs: add CONTRIBUTING.md

Author: nirbhays

CONTRIBUTING.md

@@ -0,0 +1,44 @@
+# Contributing to tokenmeter
+
+Thank you for your interest in contributing! 🎉
+
+## Getting Started
+
+1. Fork the repository
+2. Clone your fork: `git clone https://github.com/YOUR_USERNAME/tokenmeter.git`
+3. Install dev dependencies: `pip install -e ".[dev]"`
+4. Create a feature branch: `git checkout -b feature/your-feature-name`
+
+## Development
+
+```bash
+# Run tests
+pytest
+
+# Lint
+ruff check src/ tests/
+
+# Type check
+mypy src/
+```
+
+## Submitting Changes
+
+1. Ensure all tests pass: `pytest`
+2. Add tests for new functionality
+3. Update the README if your change affects usage
+4. Open a pull request with a clear description
+
+## Good First Issues
+
+Check the [issues tab](https://github.com/nirbhays/tokenmeter/issues?q=label%3A%22good+first+issue%22) for beginner-friendly tasks.
+
+## Code Style
+
+- Follow existing patterns in the codebase
+- Use type hints
+- Keep functions focused and testable
+
+## Questions?
+
+Open an issue or reach out via the repository discussions.