title: Chart.js - Vertical crosshair (vertical annotation that moves with mouse) in line graph
body: <p>I am using Chart.js and have been looking for a way to have a vertical annotation/crosshair in my graph. </p>
  
  <p>I want this vertical line to move horizontally, following my mouse cursor when the cursor is in the graph. </p>
  
  <p>How to create a vertical crosshair that changes its horizontal position based on the cursor movement using Chart.js?</p>