Function set_theme_detector 

pub fn set_theme_detector(detector: fn() -> ColorMode)

Overrides the detector used to determine whether the user prefers a light or dark theme.

This is useful for testing or when you want to force a specific color mode.

Example

use standout::{ColorMode, set_theme_detector};

// Force dark mode for testing
set_theme_detector(|| ColorMode::Dark);

// Reset to OS detection (if needed)
// Note: There's no direct way to reset to OS detection,
// but tests should restore their changes.