message: fix(docs-infra): fix vertical alignment of external link icons
  At some places external link icons appear as a subscript. For example
  https://github.com/angular/angular/blame/8366effeec8e74c1a11d2a6e1a48d42e849e4653/aio/content/guide/roadmap.md\#L37
  this commit places external link icons in the middle to improve there
  positioning in a line.
  PR Close
diff: @@ -214,7 +214,7 @@ code {
  margin-left: 2px;
  position: relative;
  @include line-height(24);
  - vertical-align: bottom;
  + vertical-align: middle;
  }
  }
  