title: Chart.js — drawing an arbitrary vertical line
body: <p>How can I draw an vertical line at a particular point on the x-axis using Chart.js?</p>
  
  <p>In particular, I want to draw a line to indicate the current day on a LineChart. Here's a mockup of the chart:
  <a href="https://i.stack.imgur.com/VQDWR.png">http://i.stack.imgur.com/VQDWR.png</a></p>
  
  <p><a href="https://i.stack.imgur.com/VQDWR.png"><img src="https://i.stack.imgur.com/VQDWR.png" alt="enter image description here"></a></p>