message: Fix rustdoc styles for very old docs
  Previously this used the selector link[type='text/css'][href*='normalize'] to inject the vendored HTML.
  Unfortunately, this selector did not exist in very old versions of rustdoc.
  Instead, this now adds the vendored.css stylesheet just before
  rustdoc.css.
diff: @@ -64,7 +64,8 @@ pub(crate) fn rewrite_lol(
  Ok(())
  };
  - // Append `vendored.css` before the first stylesheet (rustdoc's first stylesheet is `normalize.css`).
  + // Append `vendored.css` before `rustdoc.css`, so that the duplicate copy of
  + // `normalize.css` will be overridden by the later version.
  let first_stylesheet_handler = |head: &mut Element| {
  head.before(&tera_vendored_css, ContentType::Html);
  @@ -74,7 +75,7 @@ pub(crate) fn rewrite_lol(
  let (head_selector, body_selector, first_stylesheet_selector) = (
  "head".parse().unwrap(),
  "body".parse().unwrap(),
  - "link[type='text/css'][href*='normalize']".parse().unwrap(),
  + "link[type='text/css'][href*='rustdoc']".parse().unwrap(),
  );
  let element_content_handlers = vec![
  (
  