Add Two-Player Mode to Pong Game

## 🚀 Feature Request: Add Two-Player Mode

### 🔍 Overview
Currently, the Pong game is single-player (against AI). A two-player mode would allow two human players to compete using keyboard controls.

### 🎮 Expected Behavior
- Player 1 uses `W` and `S` keys to move the left paddle.
- Player 2 uses `Up Arrow` and `Down Arrow` keys to move the right paddle.
- Game continues with normal ball physics and scoring.

### 💡 Additional Notes
- Make it optional (toggle between 1P and 2P).
- Display instructions for both players before game starts.
- Highlight the active player when someone scores.

### 🏷️ GSSoC Contribution
I am a **GSSoC'25 contributor**, and would love to work on this issue. Kindly label it `GSSoC` and assign it to me if approved.