Function cast::utils::find_fave_or_alt_path

fn find_fave_or_alt_path(
    root: impl AsRef<Path>, 
    fave: &str, 
    alt: &str
) -> PathBuf

Returns the right subpath in a dir

Returns <root>/<fave> if it exists or <root>/<alt> does not exist, Returns <root>/<alt> if it exists and <root>/<fave> does not exist.