title: How to underline and bold tooltip chart js
body: <p>I have a question for a chart on my website:
  I would like to put some text on bold and underline on the Tooltip like this picture.  </p>
  
  <p>ChartJs picture:
  <a href="https://i.stack.imgur.com/mqnvT.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/mqnvT.png" alt="enter image description here"></a></p>
  
  <p>I find that it's possible to take : <em>tooltipTitleFontStyle: "bold"</em> or      <em>titleFontStyle : 'bold'</em> but none works.</p>
  
  <p>Do you have a solution for me ?</p>