title: Changing the z index of tooltip in chartjs-2
body: <p>i'm running through an issue with react-chartjs2. I want somehow to change the z-index of the tooltip. I can't find a property from the documentation so i was wondering if you know a proper solution. Here is a screenshot of my doughnut chart<a href="https://i.stack.imgur.com/FDjPT.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FDjPT.png" alt="enter image description here"></a></p>
  
  <p>You can see the issue i mentiom. Half of the tooltip is now shown. I really appreciate your help</p>
  
  <p>Here is my code:</p>
  
  <pre><code>&lt;Doughnut
          data={sectorsData}
          width={250}
          height={250}
          redraw
          options={{
            legend: {
              display: false
            },
            maintainAspectRatio: true,
            responsive: true,
            cutoutPercentage: 80,
            animation: {
              animateRotate: false,
              animateScale: false
            },
            elements: {
              center: {
                textNumber: `${sectorsCounter}`,
                text: intl.formatMessage({ id: 'pie.sectors' }),
                fontColor: '#656566',
                fontFamily: 'EurobankSans',
                fontStyle: 'normal',
                minFontSize: 25,
                maxFontSize: 25,
              }
            },
            /*eslint-disable */
            tooltips: {
              custom: (tooltip) =&gt; {
                tooltip.titleFontColor = '#656566';
                tooltip.titleFontFamily = 'EurobankSans';
                tooltip.bodyFontColor = '#656566';
                tooltip.bodyFontFamily = 'EurobankSans';
                tooltip.backgroundColor = '#eaeeef';
              },
              /* eslint-enable */
              callbacks: {
                title: (tooltipItem, data) =&gt; {
                  const titles = data.datasets[tooltipItem[0]
                    .datasetIndex].titles[tooltipItem[0].index];
                  return (
                    titles
                  );
                },
                label: (tooltipItem, data) =&gt; {
                  const labels =
                    NumberFormatter(data.datasets[tooltipItem.datasetIndex]
                    .labels[tooltipItem.index],
                    2,
                    decimalSep,
                    thousandSep
                    );
                  return (
                    labels
                  );
                },
                afterLabel: (tooltipItem, data) =&gt; {
                  const afterLabels = data.datasets[tooltipItem.datasetIndex]
                    .afterLabels[tooltipItem.index];
                  return (
                    afterLabels
                  );
                },
              },
            },
          }}
        /&gt;
  </code></pre>