feat: implement Chess Game with AI using C++ (#17)

[saumya1317]

Description

This PR implements a fully functional Chess Game with AI opponent in C++. The game features complete chess rules enforcement, an intelligent AI using Minimax algorithm with Alpha-Beta pruning, and supports both Human vs AI and Human vs Human game modes.

Key Features:

• ♟️ All 6 chess pieces with accurate movement rules
• 🤖 AI opponent with 3 difficulty levels (Easy/Medium/Hard)
• ✅ Complete rule validation (check, checkmate, stalemate)
• 🎨 Clean ASCII board display
• 📝 Algebraic notation input (e.g., "e2 e4")
• 🏗️ Object-oriented design with polymorphism and smart pointers

Technical Implementation:

• Minimax algorithm with Alpha-Beta pruning for AI decision-making
• Strategy pattern for player types (Human/AI)
• Prototype pattern for board simulation
• Cross-platform compatible (Windows/Linux/macOS)

Semver Changes

• Patch (bug fix, no new features)
• Minor (new features, no breaking changes)
• Major (breaking changes)

Issues

Closes #17

Checklist

• I have read the Contributing Guidelines.

[saumya1317]

@prajwal3114 please do check this