Function create_html_with_writer 

fn create_html_with_writer(
    time_logs: &[TimeLog],
    charts_dir: &Path,
    label_filter: Option<&HashSet<String>>,
    label_others: Option<&Label>,
    repository_name: &str,
    writer: &impl HtmlWriter,
) -> Result<(), HtmlError>

Implementation of create_html() that takes a HtmlWriter to write the file.