Revise index.html for improved layout and feature presentation

- Updated the title and overall structure of index.html to reflect the PainPain Ransomware PoC.
- Redesigned the navbar for better accessibility and user experience.
- Enhanced the hero section with a new layout and visual elements.
- Added detailed feature cards to highlight key functionalities of the application.
- Included a quick start guide and project structure overview for better onboarding.
- Updated the disclaimer for clarity on the project's ethical use.
- Replaced the demo image with a new version for improved visual representation.

Author: Mudityadev