title: Add hash to css file names
body: <p><strong>Background</strong></p>
  
  <ul>
  <li>I have two css files - styles.mobile.css and styles.desktop.css </li>
  <li>As the name suggests, I am using two separate css for mobile and desktop
  views</li>
  <li>I inject css dynamically in index.html based on screen size</li>
  <li>Obviously I can't put them in styles.css</li>
  <li>I have attached folder structure screenshot</li>
  </ul>
  
  <p><strong>Question</strong> 
  Is there a way to add hashing to styles.mobile.css and styles.desktop.css when I run ng build --prod</p>
  
  <p><strong>Code to detect device and inject css</strong></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-js lang-js prettyprint-override"><code> private addCss(): void {
      if (this.currentDevice === "desktop") {
        this.document
          .getElementById("theme")
          .setAttribute("href", "styles.desktop.css");
      } else {
        this.document
          .getElementById("theme")
          .setAttribute("href", "styles.mobile.css");
      }
    }</code></pre>
  </div>
  </div>
  </p>
  
  <p><a href="https://i.stack.imgur.com/YIWTF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YIWTF.png" alt="enter image description here"></a></p>