Add window icon support

[bennekrouf]

What changed

• Added support for setting a window icon in the Rust desktop application.
• Updated Cargo.toml to include the image crate for decoding the icon image.
• Modified src/main.rs to include a function window_icon that loads and resizes the icon image from assets/icon.png and sets it as the window icon.

Why

• To enhance the visual identity of the application by displaying a custom icon in the window title bar, taskbar, and other system areas.

How to test

• Launch the application.
• Observe the window title bar, taskbar button, and Start menu shortcut to ensure the custom icon is displayed correctly.
• Verify that the icon appears sharp and is not pixelated or blurry.