Add Space Invaders game with core mechanics

[mohit23ucs172]

🎮 Contribution: Space Invaders Project (Game #96)

I have developed an advanced Python version of the classic Space Invaders game using Pygame. Features include:

Dynamic enemy waves and boss battles

Power-ups (Rapid Fire, Spread Shot, Shield)

Particle explosions and destructible shields

Persistent high score and smooth OOP-based gameplay

Safe loading of assets (images & sounds) with fallback placeholders

All assets are organized under an assets/ folder, and the game runs with Python 3.8+ and Pygame.
Ready to play, modify, or extend! 🚀

[mohit23ucs172]

I would like to request to be assigned Project #96 – Space Invaders. I am very interested in working on this project and plan to implement an advanced Python version using Pygame with features like dynamic enemy waves, boss battles, power-ups, and smooth gameplay.