title: Dragula is not updating the dynamic list
body: <p>I am using <strong>Dragula</strong> with <strong>Angular7</strong> and dragula is not updating the list sorting even after drag and drop event successfully emitted. 
  Here, is my code :</p>
  
  <p><strong>dragula.view.html</strong></p>
  
  <pre><code>&lt;div class="portlet-content doc-portlet"&gt;
  &lt;div dragula="one-bag" [(dragulaModel)]="fileList" (dragulaModelChange)="fileList = $event"&gt;
      &lt;div class="elementline " *ngFor="let item of fileList"&gt;
          &lt;div class="extra-pages-portlet-content"&gt;
              &lt;div class="thumb-box left-col"&gt;
                  &lt;a href="{{item.file_url}}{{item.file}}" target="_blank"&gt;
                      &lt;img [src]="item.complete_url" height="100%" width="100%"&gt;
                  &lt;/a&gt;
              &lt;/div&gt;
              &lt;div class="right-col thumb-info"&gt;
                  &lt;div class="icon-row"&gt;
                      &lt;div class="icon" style="float:right;"&gt;
                          &lt;span style="cursor:grabbing; float:right;"&gt;
                              &lt;img src="../../assets/images/move.png" height="16" width="16" class="iconDelete-update"&gt;
                          &lt;/span&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
                  &lt;div class="text-and-input-field"&gt;
                    &lt;span class="text-detail-portlet" style="float:left;"&gt;Seconden: &lt;/span&gt;
                    &lt;div class="input-field"&gt;
                        &lt;input type="text" [(ngModel)]="item.slide_duration" class="text-right-Detail-user" placeholder="-" style="width:100%; text-align:right;"&gt;
                    &lt;/div&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p></p>
  
  <p><strong>dragula.component.ts</strong></p>
  
  <pre><code>dragulaService.setOptions('one-bag', {})
    dragulaService.drop.subscribe((value:any) =&gt; {
  
      var counter = 0;
       for(var j=0; j &lt; this.fileList.length;j++) {
        this.fileList[j].narrowcasting_slide_order = counter;
          counter++;
       } 
  });  
  </code></pre>
  
  <p>I am dragging and dropping the items in the list, but dragula is not updating the list sorting order. 
  Can somebody provide me any solution on this?</p>