title: ChartKick - ChartJs - Legend onClick override with default behaviour
body: <p>In my VueJs application, I present Pie-Chart &amp; table showing data. On legend onClick I am trying to filter table rows. 
  Here is my code </p>
  
  <pre><code>          &lt;pie-chart
              :donut="false"
              :data="charInfo"
              :responsive="true"
              :library="{legend:{display: true,onClick:itemSelected}}"
              legend="top"
              :colors="['#5C9AFF', '#FF3263']"/&gt;
  </code></pre>
  
  <p>Here clicking on particular legend, 'itemSelected' get called with 2 arguments, 1st is mouseEvent &amp; 2nd is legendItem.  I can get the legend text &amp; can filter table rows. But the problem is, it override default behaviour &amp; striking-out legend &amp; hide/show section of pie chart disabled.  While searching, I came across 
  <a href="https://github.com/chartjs/Chart.js/issues/2437" rel="nofollow noreferrer">ChartJs Legend onClick Issue</a>. It says to store original legend onClick event &amp; call that from my code.  I can store original onClick using something like 'const original = Chart.defaults.pie.legend.onClick', but problem is I dont have chart object to call 'original.call(,event,legendItem). And here I am sort of stuck. </p>