Extended PathBuf

Here are some examples on how to use it:

let path = Path::new("C:\\Users\\user\\Desktop\\test.txt");
let path = path.replace("user/Desktop", "user/Documents");
assert_eq!(path, PathBuf::from("C:\\Users\\user\\Documents\\test.txt"));

let path = Path::new("C:\\Users\\user\\Desktop\\test.txt");
assert!(path.contains("Desktop"));
assert!(!path.contains("Documents"));

// Windows
assert!(path.contains("user\\Desktop"));
assert!(!path.contains("user\\Documents"));

// Linux
assert!(path.contains("user/Desktop"));
assert!(!path.contains("user/Documents"));