title: keep column in front of spline lines in highchart
body: <p>is there some way to keep in front the bar column instead spline lines in a mix chart?
  If you in the attached images spline lines are in the front. I would have the lines behind of the column. is that possible?</p>
  
  <p><img src="https://i.stack.imgur.com/cBEcr.png" alt="spline line are in front of the rest of columns"></p>