title: D3.JS: Zig zag line on y-axis between zero and start value
body: <p>I've modified the <code>y.domain</code> of my D3 bar chart so it starts at a value above zero. However, I want to add a little "zig zag line" to indicate this, as in the picture below. </p>
  
  <p><a href="https://i.stack.imgur.com/5ltFW.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5ltFW.jpg" alt="Chart with zig zag line"></a></p>
  
  <p>How could I do this in D3? Many thanks!</p>