Improved Snake Water Gun Game: Modularized and added validation.

[Saurav60]

This update improves the Snake Water Gun game by:

• Refactoring into modular functions (get_computer_choice, determine_winner, etc.).
• Enhancing input validation to handle invalid user choices.
• Adding a detailed game summary at the end.
• Incorporating modern Python best practices, including type annotations and clear comments.

These changes make the game more readable, maintainable, and user-friendly.