docs: add CONTRIBUTING.md for community onboarding

Co-Authored-By: Paperclip <noreply@paperclip.ing>

Author: httpdss

CONTRIBUTING.md

@@ -0,0 +1,66 @@
+# Contributing to structkit
+
+Thank you for your interest in contributing! structkit is a YAML-first project scaffolding tool for platform engineering teams, and community contributions are what make it better.
+
+## Ways to Contribute
+
+- **Report bugs** — [open a bug report](.github/ISSUE_TEMPLATE/bug_report.md)
+- **Request features** — [open a feature request](.github/ISSUE_TEMPLATE/feature_request.md)
+- **Share your templates** — post in [GitHub Discussions](https://github.com/httpdss/structkit/discussions)
+- **Fix bugs or implement features** — see the workflow below
+- **Improve docs** — typos, examples, tutorials all welcome
+
+## Development Setup
+
+```bash
+# Clone the repo
+git clone https://github.com/httpdss/structkit.git
+cd structkit
+
+# Create a virtual environment
+python -m venv .venv
+source .venv/bin/activate  # or .venv\Scripts\activate on Windows
+
+# Install in editable mode with dev dependencies
+pip install -e ".[dev]"
+
+# Install pre-commit hooks
+pre-commit install
+```
+
+## Running Tests
+
+```bash
+pytest
+```
+
+To run a specific test file:
+
+```bash
+pytest tests/test_generate.py -v
+```
+
+## Submitting a Pull Request
+
+1. **Fork** the repo and create a branch from `main`
+2. **Make your changes** — keep PRs focused; one feature or fix per PR
+3. **Add tests** — new behavior should have test coverage
+4. **Run pre-commit** — `pre-commit run --all-files`
+5. **Open a PR** — describe what you changed and why
+
+PR title format: `type: short description` (e.g. `feat: add remote template caching`, `fix: handle empty YAML files`)
+
+## Template Contributions
+
+Have a useful structkit template? The best place to share it is [GitHub Discussions → Show your structkit templates](https://github.com/httpdss/structkit/discussions). If it's broadly useful, we may feature it in the docs.
+
+## Code Style
+
+- Python 3.9+
+- Black formatting (enforced by pre-commit)
+- Type hints encouraged for new code
+- Docstrings for public functions
+
+## Questions?
+
+Open a [GitHub Discussion](https://github.com/httpdss/structkit/discussions) — we're happy to help.