title: Add custom text to Google Visualization tooltip
body: <p>I need to add in another row of text on each of the tooltips I'm displaying (on an area chart). I've included a screenshot to illustrate what I'm hoping to do.</p>
  
  <p>My current chart:
  <img src="https://i.stack.imgur.com/2Y6wQ.gif" alt="">
  The chart with the additional text added. (This is what I'm trying to do):
  <img src="https://i.stack.imgur.com/yW4Wz.gif" alt="enter image description here"></p>
  
  <p>I'm hoping to do this without having to use a third party JS for custom tooltips. Is there any way to just add another row of text-based content to be displayed in the default tooltips?</p>
  
  <p>Any help is greatly appreciated. </p>