title: Highcharts: Adding clickable image to every xAxis gridLine
body: <p>I'm building in some custom functionality where users can click on data points in a line chart to add notes to that date. This is a bit misleading as the notes aren't actually attached to the metrics themselves but rather the date it lands on. In other words, if I have 6 series on one line chart that spans the dates 01/01/12 - 01/08/12, a single note on 01/05/12 will apply to all 6 series. So, as you can imagine clicking on a data point on one of the 6 series or the date 01/05/12 would mislead the user to believe that this note would be applied to that data point, not the entire date and any series that lands on that date.</p>
  
  <p>So, to remedy this usability issue I've decided that the best visual cue would be something like this:</p>
  
  <p><img src="https://i.stack.imgur.com/OJMR1.png" alt="enter image description here"></p>
  
  <p>There would be a clickable icon at the top of each xAxis gridLine that would need to scale with the xAxis gridLine (like if a user selects an area to zoom in on).</p>
  
  <p>Suggestions on best way to pull this off? I only need a suggestion for how best to add the icon to every line... I have all post-click functionality already built.</p>