title: Chart.js v2: make outside doughnut thicker
body: <p>I am using chart.js v2.5.0.
  I put doughnut inside doughnut.</p>
  
  <p>I want to make the outside doughnut thicker than the inside doughnuts.</p>
  
  <p>Something like this:</p>
  
  <p><a href="https://i.stack.imgur.com/iti0f.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iti0f.png" alt="enter image description here"></a></p>