docs: Created .github/CONTRIBUTING.md

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New Documentation

Created a new documentation file: .github/CONTRIBUTING.md

Description:

Document Plan: Contributing Guide

1. Welcome and Project Overview

• Brief introduction to Ax and its mission
• Link to main README and documentation
• Encourage all types of contributions (code, docs, examples, bug reports)

2. Getting Started

• Prerequisites (Node.js version, tools needed)
• Fork and clone the repository
• Install dependencies (npm install)
• Project structure overview (reference ARCHITECTURE.md for details)

3. Development Setup

• Setting up environment variables for testing (API keys)
• Running the project locally
• Using the examples for testing (npm run tsx src/examples/...)
• Development tools (TypeScript, Biome, Prettier)

4. Running Tests

• How to run unit tests (npm test)
• How to run integration tests (with real API keys)
• Test file naming conventions (.test.ts, .test-d.ts)
• Writing new tests
• Test coverage expectations

5. Coding Standards

• TypeScript best practices
• Code formatting (Biome and Prettier configs)
• Linting rules
• File naming conventions
• Import organization
• Documentation comments (for API docs generation)

6. Making Changes

• Creating a feature branch
• Commit message conventions
• Keeping changes focused and atomic
• Updating documentation when needed
• Adding examples for new features

7. Adding New Features

• How to add a new AI provider (step-by-step with reference to ARCHITECTURE.md)
• How to add new field types to signatures
• How to create custom optimizers
• How to extend AxFlow with new patterns
• Where to add examples

8. Submitting Pull Requests

• PR title and description guidelines
• Checklist before submitting (tests pass, docs updated, examples added)
• Review process expectations
• How to respond to feedback
• CI/CD checks that must pass

9. Documentation Contributions

• Where documentation lives (docs/ folder, README files)
• How to update existing docs
• How to add new guides
• Documentation style guide
• Building and previewing docs locally (if applicable)

10. Reporting Issues

• Using GitHub issue templates
• Providing reproduction steps
• Including relevant information (versions, error messages, code snippets)
• Security vulnerability reporting (reference SECURITY.md)

11. Community Guidelines

• Code of conduct expectations
• Communication channels (Discord, GitHub Discussions)
• Getting help
• Asking questions

12. Recognition

• How contributors are recognized
• Contributor list
• Release notes mentions