title: bootstrap 4 file input doesn't show the file name
body: <p>I have a problem with the custom-file-input class in Bootstrap 4.
  after I chose which file I want to upload the filename do not show.</p>
  
  <p>I use this code:</p>
  
  <pre><code>&lt;div class="input-group mb-3"&gt;
    &lt;div class="custom-file"&gt;
      &lt;input type="file" class="custom-file-input" id="inputGroupFile02"&gt;
      &lt;label class="custom-file-label" for="inputGroupFile02"&gt;Choose file&lt;/label&gt;
    &lt;/div&gt;
    &lt;div class="input-group-append"&gt;
      &lt;button class="btn btn-primary"&gt;Upload&lt;/button&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Any idea how I can fix it without getting too complicated?</p>