title: Javascript for input file button in order to notify that file upload is complete
body: <p>I am currently styling the input file buttons of my website. So far I have changed the opacity of the native input file so it doesn't display and gave it a z-index of 2 so the button is still clickable. 
  The problem is that, without the native behavior of the input file, I have no indication of when the file has finished its upload.
  How can I add a JS/JQUERY that displays a little :</p>
  
  <pre><code>&lt;i class="fa fa-check"&gt;&lt;/i&gt;
  </code></pre>
  
  <p>next to my button when the file upload is finished.</p>
  
  <p>Here's what my html looks like :</p>
  
  <pre><code> &lt;%= simple_form_for @user do |f| %&gt;
     &lt;div class="upload-file-container"&gt;
        &lt;%= f.file_field :licencepicture, id: "myFileInput" %&gt;
        &lt;div id="fileName"&gt;&lt;/div&gt;
     &lt;/div&gt;
  &lt;% end %&gt;
  </code></pre>