title: How can I always display the placeholder in mat-select intependently of the current selection
body: <p>I want the mat-select element to always show the placeholder, even if an option is selected.</p>
  
  <p>My HTML code:</p>
  
  <pre><code>&lt;mat-select [formControlName]="'language'" placeholder="Language"&gt;
      &lt;mat-option value="de"&gt;Deutsch&lt;/mat-option&gt;
      &lt;mat-option value="en"&gt;English&lt;/mat-option&gt;
  &lt;/mat-select&gt;
  </code></pre>
  
  <p>The current behavior is: A soon as a language is selected, the placeholder is made small, moved to the top and the selected language is displayed is displayed big. </p>
  
  <p>What I want to have: When a language is selected, still the placeholder should be displayed in big size, the selected language should not be shown.</p>
  
  <p>How can I do that?</p>