title: React-hook-form custom onChange handler in checkbox -> change is not registered
body: <p>I'd need to add custom handler in the onChange event of a checkbox, however, doing so onChange won't reflect to react-hook-form.</p>
  <p>I've followed the instructions how to do custom <code>onChange</code> by following the chapter</p>
  <p><em>Custom onChange, onBlur</em>: ​ <a href="https://react-hook-form.com/api/useform/register/" rel="nofollow noreferrer">https://react-hook-form.com/api/useform/register/</a></p>
  <p>However cannot make it work.</p>
  <p>Seeing in the <em>DevTool</em> the first checkbox change reflects to form just fine however the latter with a custom handler does not.</p>
  <pre><code>...
  const subscribeToNewsLetter = register('subscribeToNewsLetter')
  ...
  &lt;div&gt;
    ​&lt;label&gt; I consent &lt;/label&gt;
    ​&lt;input            
      ​type=&quot;checkbox&quot;
      ​{...register('consent')}  //This checkbox without any custom handler works fine
    ​/&gt;
  ​&lt;/div&gt;
  
  ​&lt;div&gt;
    ​&lt;label&gt;Subscribe to newsletter&lt;/label&gt;
    ​&lt;input            
      ​type=&quot;checkbox&quot;
      ​onChange={(e) =&gt; {
        ​subscribeToNewsLetter.onChange(e); // This needs to do custom stuff in onChange
        ​handleChange(e);         // However doing so 
      ​}}                         // the change is not registered to hook-form
      ​onBlur={subscibeToNewLetter.onBlur}
      ​ref={subscibeToNewLetter.ref} 
    ​/&gt;
  &lt;/div&gt;
  ...
  </code></pre>
  <p>I've been fiddling it here which illustrates the problem the best.
  <a href="https://stackblitz.com/edit/react-hook-form-fiddling-zlnhzs" rel="nofollow noreferrer">https://stackblitz.com/edit/react-hook-form-fiddling-zlnhzs</a></p>