Currently, README.md is rendered using comark::Options::default() (src):

if ext == "md" {
  markdown_to_html(
    &std::fs::read_to_string(entry.path())?,
    &ComrakOptions::default(),
  )
}

Thus, common structures like table are not rendered. It would be convenient to enable some of the extensions in comrak::options::Extension.

For backward compatibility, maybe add an argument --readme-extensions and let users choose which extension is enabled.