title: Formly Form loading hanging site performance
body: <p>I have implemented complex custom wrapper.
  If the FORM contain 10+ custom wrapper it is hanging HTML UI page for some seconds.</p>
  <p>For example when ng-if is true, 5+ seconds HTML hanged.</p>
  <pre><code>  &lt;form [formGroup]=&quot;form&quot; *ngIf=&quot;showForm &amp;&amp; fields &amp;&amp; model&quot;&gt;
      &lt;formly-form [model]=&quot;model&quot; [fields]=&quot;fields&quot; [options]=&quot;options&quot; [form]=&quot;form&quot;
        (modelChange)=&quot;onModelChange($event)&quot;&gt;&lt;/formly-form&gt;
    &lt;/form&gt;
  </code></pre>
  <p>Is there any Event when the FORM loading is completed?
  Can we run it in web worker?</p>