title: Make Angular dialog draggable only by title
body: <p>I've already done this:</p>
  <pre><code>&lt;div mat-dialog-title
       cdkDrag
       cdkDragRootElement=&quot;.cdk-overlay-pane&quot;
       cdkDragHandle&gt;
  &lt;/div&gt;
  </code></pre>
  <p>But the solution causes the dialog to be draggable by clicking any place of the window which makes impossible to extend <code>&lt;textarea&gt;</code> within the content block.
  Ideally I need a way to make it draggable only by clicking the title.</p>