Add CONTRIBUTING.md guide for community contributors

- Comprehensive contribution guidelines for ProxySQL
- Includes development setup, coding standards, and PR guidelines
- Provides clear instructions for bug reports and feature requests

CONTRIBUTING.md

@@ -0,0 +1,103 @@
+# Contributing to ProxySQL
+
+Thank you for your interest in contributing to ProxySQL! We welcome contributions from the community.
+
+## Code of Conduct
+
+We expect all contributors to be respectful and constructive. Please help us maintain a welcoming environment for everyone.
+
+## Before You Start
+
+Discuss major changes: For significant features or architectural changes, please open an issue first to discuss.
+
+Check existing issues: Someone might already be working on something similar.
+
+Reference issues: When fixing bugs or implementing requested features, mention the issue number in your PR.
+
+## Development Setup
+
+ProxySQL provides Docker build images for development. The required packages for building are listed in the Dockerfiles at: https://github.com/ProxySQL/docker-images/tree/main/build-images
+
+For example, to see packages needed for Ubuntu 24.04, check: https://github.com/ProxySQL/docker-images/blob/main/build-images/build-ubuntu24/Dockerfile
+
+## Making Changes
+
+- Fork the repository
+- Create a feature branch: `git checkout -b feature/your-feature-name`
+- Make your changes
+- Ensure your code builds successfully
+- Submit a Pull Request
+
+## Coding Standards
+
+Follow the existing code style and patterns in the codebase
+
+Use clear, descriptive names for variables and functions
+
+Add comments for complex logic
+
+Keep functions focused and maintainable
+
+### For C++ Code:
+
+- Use C++11/14 features appropriately
+- Follow RAII principles for resource management
+- Consider performance implications (ProxySQL is performance-critical)
+
+## Testing
+
+All PRs will go through our automated testing suite. While the full testing framework isn't publicly available, we encourage you to test your changes as thoroughly as possible.
+
+## Commit Messages
+
+Recommendations (not strict requirements):
+
+- Use descriptive messages that explain what changed and why
+- Reference issue numbers when applicable (`#123`)
+- Keep the first line under 72 characters
+
+**Example:** `Fix memory leak in connection pooling (#456)`
+
+## Pull Request Guidelines
+
+- Use a clear title and description
+- Explain what was changed and why
+- Note any breaking changes or performance impacts
+- Update documentation if functionality changes
+
+## Reporting Bugs
+
+Please include in bug reports:
+
+- ProxySQL version
+- Steps to reproduce
+- Expected vs actual behavior
+- Relevant configuration details
+- Logs (with sensitive data redacted)
+
+## Feature Requests
+
+For new features, please:
+
+- Describe the feature/problem clearly
+- Explain the use case
+- Consider performance implications
+- Note any backward compatibility concerns
+
+## Questions and Support
+
+- **Mailing list**: Join the ProxySQL mailing list for discussions
+- **GitHub issues**: Use GitHub issues for questions, bugs, and feature requests
+- **Search existing issues** before creating new ones
+
+## Recognition
+
+Contributors will be credited in the release notes for their contributions.
+
+## License
+
+By contributing to ProxySQL, you agree that your contributions will be licensed under the project's GPLv3 license.
+
+---
+
+Thank you for helping make ProxySQL better!