Add comprehensive CONTRIBUTING.md file to guide potential contributors

[Copilot]

This PR adds a comprehensive CONTRIBUTING.md file to provide clear guidance for potential contributors on how to effectively contribute to the terraform-module-releaser project.

What's included

The CONTRIBUTING.md file covers all essential aspects of the contribution process:

• Development Environment Setup: Prerequisites (Node.js 20+, npm, Git) and initial setup instructions
• Development Workflow: Step-by-step guide for making changes, including branch creation and testing
• Commit Message Guidelines: Detailed explanation of conventional commits format used by the project
• Testing Instructions: How to run tests with vitest and handle different test types
• Code Style and Linting: Guidelines for using Biome for code formatting and linting
• Pull Request Process: Complete workflow from creating PRs to addressing review feedback
• Issue Reporting: Templates for bug reports, feature requests, and security issues
• Community Guidelines: Code of conduct and communication standards
• Release Process: Information about the automated release workflow

Key features

• References existing project tools and workflows without creating new dependencies
• Follows the same professional documentation style as README.md and SECURITY.md
• Includes practical examples and code snippets for clarity
• Provides links to relevant external resources (Conventional Commits, GitHub guidelines)
• Formatted according to the project's markdown standards (prettier, textlint)

The file integrates seamlessly with the existing project structure and maintains consistency with the established documentation patterns. It will help streamline the contribution process and improve the collaboration experience for both new and existing contributors.

Fixes #10.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• terraform-docs.io
  • Triggering command: /usr/bin/curl -sSLfo ./terraform-docs.tar.gz REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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