Update README.md

Added the initial version of the README.md, adapted from the CO2NEX whitepaper (v1.0 – May 2025). 

This document outlines CO2NEX’s core vision, problems addressed, and our integrated solution for real-time carbon credit verification at planetary scale. It details the platform architecture, tech stack, roadmap (2024–2027), business model, and trading logic.

The README is optimized for GitHub readability and transparency, while protecting sensitive IP. It serves as the public-facing entry point for collaborators, developers, and potential partners.

Next steps may include adding:
- Links to white-label SDKs/APIs
- Live roadmap sync
- Contribution guidelines
- Technical documentation structure