title: Change the size of modal in ngDialog
body: <p>does ngDialog allow different sizes of modal?</p>
  
  <p>For example, bootstrap-angular modal has such function:</p>
  
  <pre><code>$modal.open('sm') or $modal.open('lg')
  </code></pre>
  
  <p>which will open small and large modals respectively.</p>
  
  <p>Is there such thing in ngDialog?</p>