Function write_md 

pub fn write_md(
    out_path: &str,
    files: &[PathBuf],
    id_map: &HashMap<PathBuf, String>,
    tree_text: Option<String>,
    id_style: &str,
    watermark: &str,
    command_str: &Option<String>,
    stamp: &str,
    suffix_stamp: bool,
    title_file: &str,
    title_file_with_path: bool,
) -> Result<()>