title: With Angular Material Dialog, how to add multiple classes to the dialog?
body: <p>I can add a custom class to a MatDialog this way:</p>
  <pre><code>    this.dialog.open(MyGreatDialogComponent, {
        data: myGreatData,
        panelClass: 'my-great-class',
      });
  </code></pre>
  <p>Is it possible to add an additional class(es) to a Material dialog?</p>