title: How to custom input file with bootstrap 4
body: <p>I want to do like this in webpack bootstrap 4 env :</p>
  
  <p><a href="http://v4-alpha.getbootstrap.com/components/forms/#custom-forms" rel="noreferrer">http://v4-alpha.getbootstrap.com/components/forms/#custom-forms</a></p>
  
  <p><strong>File browser</strong></p>
  
  <pre><code>&lt;label class="custom-file"&gt;
    &lt;input type="file" id="file" class="custom-file-input"&gt;
    &lt;span class="custom-file-control"&gt;&lt;/span&gt;
  &lt;/label&gt;
  </code></pre>
  
  <p>How to override the <strong>"placeholder"</strong>  and <strong>"button-label"</strong> value</p>