docs: Add contributor quick-start guide

New file providing step-by-step onboarding for contributors:
- Quick links to contributor manual, coding standards, and testing philosophy
- 8-step workflow from fork to pull request
- Code of conduct principles (respectful, constructive, welcoming)
- Clear acceptance criteria (type stability, tests, documentation, clean commits)
- Rejection criteria (type instability, no tests, Greek letters, breaking changes)
- Help resources (discussions, issues, PRs)
- MIT license acknowledgment

docs/CONTRIBUTING.md

@@ -0,0 +1,99 @@
+---
+title: "Contributing to JuliaFEM"
+description: "Quick start guide for new contributors"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["development", "contributing", "getting started"]
+keywords: ["juliafem", "contributing", "pull requests", "development"]
+audience: "contributors"
+level: "beginner"
+type: "guide"
+---
+
+Thank you for considering contributing to JuliaFEM! 🎉
+
+## Quick Links
+
+- **[Contributor Manual](contributor/README.md)** - Start here for technical details
+- **[Coding Standards](contributor/coding_standards.md)** - **REQUIRED** reading for all contributors
+- **[Testing Philosophy](contributor/testing_philosophy.md)** - How we test and why
+
+## Quick Start
+
+1. **Fork the repository** on GitHub
+
+2. **Clone your fork:**
+
+   ```bash
+   git clone https://github.com/YOUR_USERNAME/JuliaFEM.jl.git
+   cd JuliaFEM.jl
+   ```
+
+3. **Create a branch:**
+
+   ```bash
+   git checkout -b fix-issue-123
+   ```
+
+4. **Read the [Coding Standards](contributor/coding_standards.md)** - Critical rules like:
+   - ✅ Use `u, v, w` for reference coordinates
+   - ❌ Never use Greek letters (ξ, η, ζ) in code
+   - ✅ Type-stable code required
+   - ✅ Zero allocations in hot paths
+
+5. **Make your changes** following the standards
+
+6. **Run tests:**
+
+   ```bash
+   julia --project=. -e 'using Pkg; Pkg.test()'
+   ```
+
+7. **Commit with good messages:**
+
+   ```text
+   feat(topology): Add Pyr5 pyramid element
+   
+   - Implement 5-node pyramid reference element
+   - Zero-allocation tuple interface
+   - Tests for reference coordinates
+   
+   Closes #123
+   ```
+
+8. **Push and create Pull Request**
+
+## Code of Conduct
+
+- Be respectful and constructive
+- Focus on the code, not the person
+- Welcome newcomers and help them learn
+- Ask questions before making assumptions
+
+## What We Look For
+
+✅ **Type-stable code** - Performance depends on it  
+✅ **Tests included** - New features need tests  
+✅ **Documentation** - Docstrings for exported functions  
+✅ **Clean commits** - Logical, well-described changes  
+✅ **Follows standards** - Read [coding_standards.md](contributor/coding_standards.md)  
+
+❌ **Type-unstable code** - Will be rejected  
+❌ **No tests** - Cannot merge without tests  
+❌ **Greek letters in code** - Use u, v, w instead  
+❌ **Breaking changes** - Discuss in issue first  
+
+## Getting Help
+
+- **Questions?** Open a GitHub Discussion
+- **Bug report?** Open an issue with reproducible example
+- **Feature idea?** Open an issue to discuss before implementing
+- **Stuck?** Ask in the issue or PR - we're happy to help!
+
+## License
+
+By contributing, you agree that your contributions will be licensed under the MIT License.
+
+---
+
+**Ready to contribute?** → Start with [Contributor Manual](contributor/README.md) and [Coding Standards](contributor/coding_standards.md)