title: ::placeholder::after doesn't work in CSS
body: <p>When I apply <code>::after</code> for my <code>&lt;p&gt;</code> element, it works fine, but when I use it for the <code>::placeholder</code> pseudo-element on my input fields, it doesn't work:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>p::after {
    content: "*";
    color: red;
  }
  
  #registerFirstName::placeholder::after {
    content: "*";
    color: red;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
    &lt;body&gt;
      &lt;input id="registerFirstName" tabindex="1" name="registerFirstName" title="" alt="" value="" required="required" maxlength="40" aria-required="true" placeholder="First Name" class="error" aria-invalid="true" type="text"&gt;
  
      &lt;p&gt;I live in Ducksburg&lt;/p&gt;
    &lt;/body&gt;
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>Output:</p>
  
  <p><a href="https://i.stack.imgur.com/bYf2H.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/bYf2H.png" alt="enter image description here"></a></p>
  
  <p>Can someone help me fixing this?</p>