Add contributing guide for developers

CONTRIBUTING.md

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+# Contributing to PyHamcrest
+
+Thank you for your interest in contributing to PyHamcrest! This guide will help you get started.
+
+## Table of Contents
+
+- [Development Setup](#development-setup)
+- [Running Tests](#running-tests)
+- [Code Style and Linting](#code-style-and-linting)
+- [Type Checking](#type-checking)
+- [Adding Changelog Entries](#adding-changelog-entries)
+- [Submitting Pull Requests](#submitting-pull-requests)
+- [Release Process](#release-process-for-maintainers)
+
+## Development Setup
+
+### Prerequisites
+
+- Python 3.10 or later (Python 3.14 recommended for development)
+- Git
+
+### Installation
+
+1. Fork and clone the repository:
+
+```bash
+git clone https://github.com/YOUR-USERNAME/PyHamcrest.git
+cd PyHamcrest
+```
+
+2. Install development dependencies:
+
+We recommend using [uv](https://github.com/astral-sh/uv) for fast dependency resolution:
+
+```bash
+pip install uv
+uv pip install -e ".[dev]"
+```
+
+Or using pip directly:
+
+```bash
+pip install -e ".[dev]"
+```
+
+3. Install pre-commit hooks:
+
+```bash
+pre-commit install
+```
+
+This ensures code style checks run automatically before each commit.
+
+## Running Tests
+
+### Quick Test Run
+
+Run tests with pytest:
+
+```bash
+pytest
+```
+
+Run a specific test file:
+
+```bash
+pytest tests/hamcrest_unit_test/core/isequal_test.py
+```
+
+Run a specific test:
+
+```bash
+pytest tests/hamcrest_unit_test/core/isequal_test.py::TestClass::test_name
+```
+
+### Test Coverage
+
+Run tests with coverage:
+
+```bash
+coverage run -m pytest
+coverage report
+```
+
+### Testing Across Python Versions
+
+We use [tox](https://tox.wiki/) to test across multiple Python versions:
+
+```bash
+# Test all available Python versions (skips missing interpreters)
+tox -s
+
+# Test specific Python version
+tox -e py312
+
+# Test with numpy support
+tox -e py312-numpy
+```
+
+**IMPORTANT**: Always run `tox -s` before submitting a pull request to verify tests pass across all available Python versions. The `-s` flag skips missing interpreters.
+
+### Supported Python Versions
+
+- Python 3.10, 3.11, 3.12, 3.13, 3.14
+- PyPy 3.11
+
+## Code Style and Linting
+
+PyHamcrest uses automated code formatting and linting:
+
+### Auto-formatting
+
+Code is formatted with [Black](https://black.readthedocs.io/) and [Ruff](https://docs.astral.sh/ruff/).
+
+Run pre-commit hooks on all files:
+
+```bash
+pre-commit run --all-files
+```
+
+Or via tox:
+
+```bash
+tox -e lint
+```
+
+### Style Notes
+
+- Line length: 100 characters
+- The codebase intentionally uses star imports (`from module import *`) to provide a clean public API
+- Import order is managed by isort with a custom "hamcrests" profile
+
+## Type Checking
+
+PyHamcrest includes type annotations and is checked with [mypy](https://mypy-lang.org/).
+
+Run type checking:
+
+```bash
+mypy src/
+```
+
+Or via tox:
+
+```bash
+tox -e typing
+```
+
+### Type Hint Tests
+
+Type hints are tested using mypy with special test files in `tests/type-hinting/`. These files use a YAML format to test that type annotations work correctly. If you're adding or modifying type annotations, consider adding corresponding type tests.
+
+## Adding Changelog Entries
+
+**REQUIRED**: Every pull request that changes functionality must include a changelog entry.
+
+**Exception**: Documentation-only changes (README, CONTRIBUTING, etc.) do not require changelog entries.
+
+PyHamcrest uses [towncrier](https://towncrier.readthedocs.io/) to manage the changelog.
+
+### How to Add a Changelog Entry
+
+For every PR that changes code or functionality, create a changelog fragment file in the `changelog.d/` directory:
+
+**Format**: `changelog.d/{issue_or_pr_number}.{category}.rst`
+
+**Categories**:
+- `feature` - New features or enhancements
+- `bugfix` - Bug fixes
+- `misc` - Miscellaneous changes (CI, docs, refactoring, etc.)
+
+**Example**: If your PR is #123 and adds a new feature, create:
+
+`changelog.d/123.feature.rst`:
+```rst
+Add support for matching custom objects with has_attributes matcher.
+```
+
+**Tips**:
+- Keep descriptions concise and user-focused
+- Write in the past tense ("Added", "Fixed", not "Add", "Fix")
+- Don't include implementation details unless relevant to users
+- The issue/PR number in the filename will be automatically linked in the generated changelog
+
+## Submitting Pull Requests
+
+### Before Submitting
+
+1. ✅ Run tests: `tox -s`
+2. ✅ Run linting: `pre-commit run --all-files`
+3. ✅ Run type checking: `tox -e typing`
+4. ✅ **Add changelog entry (REQUIRED for code changes)** - see [Adding Changelog Entries](#adding-changelog-entries)
+5. ✅ Update documentation if needed
+
+### CI Checks
+
+When you create a pull request, GitHub Actions will automatically run:
+
+- Tests on Python 3.10, 3.11, 3.12, 3.13, 3.14, and PyPy 3.11
+- Tests on Linux, macOS, and Windows
+- Linting checks
+- Type checking
+- Documentation build
+
+The CI workflow runs on:
+- All pull requests to `main` or `master`
+- Pushes to `main`, `master`, or branches starting with `ci-testing-*`
+
+### PR Guidelines
+
+- **Branch naming**: Use descriptive names like `fix-issue-123` or `add-new-matcher`
+- **Commit messages**: Write clear, descriptive commit messages
+- **PR description**: Explain what changes you made and why
+- **Link issues**: Reference related issues in your PR description (e.g., "Fixes #123")
+- **Keep PRs focused**: One feature or fix per PR makes review easier
+
+## Release Process (for Maintainers)
+
+PyHamcrest uses automated releases via git tags.
+
+### Creating a Release
+
+1. Ensure all PRs for the release are merged to `main`
+
+2. Run the release script:
+
+```bash
+./release.sh V2.2.0
+```
+
+This script:
+- Creates a git tag (e.g., `V2.2.0`)
+- Runs `towncrier build` to generate the changelog from fragments in `changelog.d/`
+- Re-tags to include the changelog changes
+- Prompts you to push the tag
+
+3. Push the tag to trigger the release:
+
+```bash
+git push origin --tags "V2.2.0"
+```
+
+4. GitHub Actions automatically:
+- Builds the package (wheel and sdist)
+- Publishes to PyPI using trusted publishing
+- Creates a GitHub release
+
+### Versioning
+
+- Format: `V{major}.{minor}.{patch}` (e.g., `V2.1.0`)
+- Version is automatically derived from git tags using [hatch-vcs](https://github.com/ofek/hatch-vcs)
+- No manual version bumping needed in code
+
+## Questions?
+
+If you have questions or need help:
+
+- 💬 [Open a discussion](https://github.com/hamcrest/PyHamcrest/discussions)
+- 🐛 [Report an issue](https://github.com/hamcrest/PyHamcrest/issues)
+
+Thank you for contributing! 🎉