Function render_udvt 

fn render_udvt<'ast>(
    span: Span,
    u: &'ast ItemUdvt<'ast>,
    docs: &'ast DocComments<'ast>,
    ctx: &Ctx<'_>,
    name_to_page: &NameToPage,
    page_path: &Path,
    git_url: Option<&str>,
) -> String