Rebuilt project documentation with detailed README, architecture workflows, and onboarding guides

[Mausam5055]

📝 Summary

The previous README.md was too brief and lacked the necessary context for new contributors to easily onboard. This PR provides a complete overhaul, essentially building out the documentation from scratch. By reading the new README, new interns or developers will now have a complete, immediate understanding of the project without needing to manually inspect the codebase.

🚀 Key Additions

1. Comprehensive README Overhaul

• Project Details: Added complete, detailed explanations of the project's purpose and features.
• Folder Structure Breakdown: Documented the entire directory structure, explicitly defining the purpose and contents of every major folder in the repository so new contributors know exactly where to look.
• Architecture Overview: Introduced clear architectural documentation to explain how the different systems interact.

2. Dedicated Architecture Guide

• Created a new ARCHITECTURE.md file to host complex flowcharts and diagrams without cluttering the main README.
• Documented all core workflows, including KiCad-to-Ngspice conversion and Mixed-Signal pipelines.

3. Contributing Page Enhancements

• Restructured CONTRIBUTING.md to properly guide new developers.
• Added detailed, organized sections for Active and Major Contributors.
• Integrated a dynamic Repository Growth & Activity graph to visually showcase community contributions.

4. Security Policy Update

• Replaced the empty SECURITY.md placeholder with a robust, professional security policy, including proper disclosure guidelines and supported version matrices.

📸 Impact

These updates transform the repository's documentation into a fully comprehensive guide. It will drastically reduce the friction for new developers trying to understand the architecture, folder layout, and contribution processes of the project.