Add CONTRIBUTING.md file

[Copilot]

This PR adds a comprehensive CONTRIBUTING.md file to help new and existing contributors understand how to effectively contribute to the memfs project.

What's included

The CONTRIBUTING.md file provides detailed guidance on:

• Getting Started: Prerequisites (Node.js 4.0.0+, Yarn, Git) and repository setup
• Development Workflow: All available scripts including yarn build, yarn test, yarn tslint, and yarn prettier
• Code Style: TypeScript, Prettier, and TSLint configuration details
• Commit Messages: Conventional Commits format with examples
• Pull Request Process: Comprehensive checklist and requirements
• Issue Reporting: Guidelines for effective bug reports and feature requests
• Project Structure: Overview of the codebase organization

Why this matters

Having clear contribution guidelines helps:

• Reduce onboarding time for new contributors
• Ensure consistent code quality and commit message format
• Streamline the review process for maintainers
• Create a welcoming environment for open source participation

The file is tailored specifically to memfs's toolchain and development practices, referencing the existing CODE_OF_CONDUCT.md and linking to the comprehensive documentation in the docs/ directory.

Structure

The document includes a table of contents for easy navigation and follows common open source contribution guide best practices, making it familiar to developers experienced with GitHub projects.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.