title: How to add vertical lines to graph with HighStocks or HighCharts?
body: <p>I have successfully created a chart with HighChart's HighStock. I'm trying to add vertical lines to the chart. I've searched everywhere in HighStock's docs, Stackoverflow and Google on how to do this, but to no avail. I tried HighStock's "flags" but can't create vertical lines with them.</p>
  
  <p>I basically want to turn this chart...
  <a href="https://i.stack.imgur.com/5j5nS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5j5nS.png" alt="Charts with no lines"></a></p>
  
  <p>... into something like this:
  <a href="https://i.stack.imgur.com/uIfyS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uIfyS.png" alt="enter image description here"></a></p>
  
  <p>Is this even possible? If yes, how? Thanks!</p>