Top-level class documentation
<p>Rubycop outputs messages like:</p>

<pre><code>app/controllers/welcome_controller.rb:1:1: C: Missing top-level class documentation comment.
class WelcomeController &lt; ApplicationController
^^^^^
</code></pre>

<p>I wonder what does top-level class documentation look like. It's not just a comment, is it? It needs to have a special format, but which one?</p>