title: How to show the optgroup value + option value as the selection
body: <p>Take a look at the following select:</p>
  
  <pre><code>&lt;select&gt;
  &lt;optgroup label="A"&gt;
  &lt;option value=""&gt;1&lt;/option&gt;
  &lt;option value=""&gt;2&lt;/option&gt;
  &lt;option value=""&gt;3&lt;/option&gt;
  &lt;optgroup label="B"&gt;
  &lt;option value=""&gt;4&lt;/option&gt;
  &lt;option value=""&gt;5&lt;/option&gt;
  &lt;option value=""&gt;6&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>When any element is selected I would like to display its label + value in the selection instead of just value. So if 4 is selected I would like the selection to show B - 4</p>