Update README.md and AppIcon assets

- Corrected formatting in README.md for clearer project structure representation.
- Updated AppIcon assets by adding multiple sizes and resolutions (16x16, 32x32, 128x128, 256x256, and 512x512) along with their @2x variants, improving visual representation across different display settings.

These changes enhance documentation clarity and application icon quality.

README.md

@@ -149,7 +149,7 @@ git push origin v1.0.0
 ```
 TypeSwitch/
 ├── Project.swift       # Tuist project configuration
-├─�� Tuist/             # Tuist configuration files
+├── Tuist/             # Tuist configuration files
 ├── Sources/           # Source code
 │   ├── Models/        # Data models
 │   ├── Views/         # SwiftUI views