title: h1 custom border-bottom width instead of full-width
body: <p>This is what I need:</p>
  
  <p><a href="https://i.imgur.com/wwHqO4M.png" rel="nofollow noreferrer"><img src="https://i.imgur.com/wwHqO4M.png" alt="enter image description here"></a></p>
  
  <p>This is what I have:</p>
  
  <pre><code>h1 {
      border-bottom: 3px solid red;
  }
  </code></pre>
  
  <p>and the borders are full-width...</p>
  
  <p>Is there a nice solution?</p>