title: Dropzone is not defined, with webpack on symfony
body: <p>I watched the various conversations on the subject, sorry to redo a topic but I look for a whole day and I do not understand why Dropzone is not defined.</p>
  
  <p>In my console it's always the same speech ...
  <strong><em>Uncaught ReferenceError: Dropzone is not defined</em></strong></p>
  
  <p>Where could I have been wrong?</p>
  
  <pre><code>&lt;div action="{{path('document_create')}}" class="dropzone"&gt;
         &lt;div class="fallback"&gt;
                {{ form_widget(form.file, {
                    'attr': {'type': 'file', 'name': 'file'}
                }) }}
         &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>JS:</p>
  
  <pre><code>Dropzone.autoDiscover = false;
  
                  $(function() {
                      //Dropzone class
                      var myDropzone = new Dropzone(".dropzone", {
                          url: "upload.php",
                          paramName: "file",
                          maxFilesize: 2,
                          maxFiles: 10,
                          acceptedFiles: "image/*,application/pdf"
                      });
  
                      $('#startUpload').click(function(){           
                          myDropzone.processQueue();
                      });
                  });
  </code></pre>