Add Smart Plantation project to README

[sushantkumarkhobian-lab]

📝 Description

This PR introduces the Smart Plantation Platform under the README.md Projects section. It is an end-to-end smart agriculture solution combining hardware telemetry processing, automated irrigation control loops, an ML inference engine, and a real-time full-stack dashboard workspace.

🛠️ Components Added

• Firmware: Core microcontroller loop tracking DHT22, soil moisture, rain gauges, and float switches alongside SHA256 integrity hashing checks.
• Full-Stack Dashboard: React (Vite) interface combined with a robust Node.js Express server connected to MongoDB.
• AI Analysis Engines: Python scripts processing crop yield optimization models and CNNs for plant pest/disease detection.
• Documentation: Includes high-definition architecture block diagrams, wiring schemes, user dashboard outputs, and live physical hardware layout photographs.

✅ Checklist

• Project placed correctly inside the ESP32/ directory.
• Clear folder architecture matching repo standard specifications.
• Full bill of materials listed within requirements.txt.
• Verified code compiles and executes smoothly locally without overlapping dependency errors.