Function render_html_timeline 

pub fn render_html_timeline(
    data: &TimelineData,
    output_path: &Path,
    stems_dir: Option<&Path>,
    slug: &str,
    tag: &str,
    layers_dir: Option<&Path>,
) -> Result<()>

render_html_timeline(data, output_path, stems_dir, slug=, tag=, layers_dir=).