ProgressBar for flickity

gistfile1.txt

add div.progressbar into slider's container
add option 'cellSelector'

and add some callbacks :

 $gallery.on( 'cellSelect', function() {
  var el = $('.progressbar');
   var  newone = el.clone(true);
        el.before(newone);
 $("." + el.attr("class") + ":last").remove();
 })
 
 style for progressBar: 
 .progressbar{
    height: 7px;
    background-color: #fff;
    border: 1px solid #7b1b1b;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    z-index: 2;
    &::before{
      content: '';
      display: block;
      height: 100%;
      animation: progressBar 4s;
      background-color: #7b1b1b;
    }
  }
  @keyframes progressBar {

  0%  {width: 0%;}
  100%{width: 100%;}
}

option ' autoPlay' must be equal to animation duration parameter