Macro println_warning 

macro_rules! println_warning {
    ($($arg:tt)*) => { ... };
}

Prints a warning message with yellow background and white text.

Supports format string syntax like format! macro:

• println_warning!("Warning") - Simple string
• println_warning!("Warning: {}", error) - Positional arguments
• println_warning!("Warning: {error}") - Named arguments (Rust 1.58+)