fix. Handle missing trailing slash for the Windows drive path.

[albertleigh]

Handle missing trailing slash for Windows drive paths.

Added a special case to re-append a trailing backslash (\) for Windows drive paths like C: to ensure correct absolute path handling. A new test verifies this behavior by validating path consistency after transformations.

And I added a test case trying to explain everything:

#[test]
#[cfg(feature = "std")]
#[cfg(windows)]
fn extend_empty_segment_to_win_driver() {
    let path_str = r"C:\";
    let prefix_path = PathBuf::from(r"C:\");
    let prefix_path = std::fs::canonicalize(prefix_path).expect("Failed to canonicalize path");
    let mut url = Url::from_file_path(prefix_path).expect("Failed to parse path");
    let empty_segment: [&str; 0] = [];

    url.path_segments_mut()
        .expect("url path")
        .pop_if_empty()
        .extend(empty_segment);

    let path = url
        .to_file_path()
        .expect("Failed to parse the windows driver path");
    assert_eq!(path.to_str(), Some(path_str));
}

Not sure I got it fixed at a right place, please kindly help review. Thanks 😁