title: Vue Chart JS and options reactivity
body: <p>I'm trying to recreate the doughnut to pie change in behavior as seen here: 
  <a href="https://www.chartjs.org/samples/latest/scriptable/pie.html" rel="nofollow noreferrer">https://www.chartjs.org/samples/latest/scriptable/pie.html</a></p>
  
  <p>I'm using VueJS version of Chart JS and after recreating this it seems to not be reactive at all.</p>
  
  <p>Here is the method that I use to change the chart to the other one:</p>
  
  <pre><code>togglePieDoughnut() {
    this.options.cutoutPercentage = 50;
  }
  </code></pre>
  
  <p>As you can see it does not work as intended, even tough I used reactiveprop mixin.</p>
  
  <p><a href="https://codesandbox.io/s/vue-chartjs-demo-jqk2h?file=/src/App.vue:298-371" rel="nofollow noreferrer"><img src="https://codesandbox.io/static/img/play-codesandbox.svg" alt="Edit Vue Chart.js add label"></a></p>
  
  <p>EDIT: To be precise I want to recreate the chart update behaviour as seen in the example on chartjs.org website. I do not want to rerender the chart, rather update it so the transition remains smooth.</p>