title: Show a select field only when a specific element was chosen from another select element list
body: <p>I am wondering how to achieve this.</p>
  <p>I have a list of types. Depending on a chosen type, either another select element will appear in the form or not.</p>
  <p>For example, if type Page or Collection are chosen, another select field will appear under, listing all the pages.</p>
  <p>For now I have this and I am not sure how to achieve my goal.</p>
  <pre><code>   &lt;div class=&quot;form-group mb-3&quot;&gt;
       &lt;div&gt;
           &lt;%= select f, :type, [&quot;Page&quot;: 1, &quot;Category&quot;: 2, &quot;Collection&quot;: 3, &quot;Link&quot;: 4], placeholder: &quot;Choose a type&quot;%&gt;
           &lt;%= error_tag f, :type %&gt;
       &lt;/div&gt;
     &lt;/div&gt;
  </code></pre>