A instructions panel above pong game

### 🚀 Feature Request

**What would you like to be added?**
A styled instructions box above the game canvas that shows basic controls (e.g. "W/S = left paddle", "↑/↓ = right paddle") and a short game description.

**Why is this useful?**
- Helps new players understand controls instantly.
- Improves visual structure and user experience.
- Involves only HTML and CSS (no JavaScript changes).