title: Chart.js reverse Y axes but keep background fill underneath line
body: <p>I am trying to plot data using chart.js and want my data to be high to low, so that the top of the Y axes is 0 and the bottom is my highest number.</p>
  
  <p>I've used the <code>reverse</code> option for the axes, but this has meant that my background fill has also inverted. I can't figure out a way to get this to work so that my fill is still underneath the line when the axes is reversed.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code> var ctx = document.getElementById("diaryChart").getContext('2d');
          var myChart = new Chart(ctx, {
              type: 'line',
              data: {
                  labels: ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"],
                  datasets: [{
                      label: 'Position in company',
                      data: [12, 19, 3, 5, 2, 3, 7, 8, 13, 10, 5, 2],
                      backgroundColor: [
                          'rgba(50, 66, 92, 0.3)'
                      ],
                      borderColor: [
                          'rgba(0, 0, 0,1)'
                      ],
                      borderWidth: 3
                  }]
              },
              options: {
                  scales: {
                      yAxes: [{
                          display: false,
                          ticks: {
                              beginAtZero: true,
                              reverse: true,
                              start: 0
                          }
                      }]
                  }
              }
          });</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.2/Chart.bundle.js"&gt;&lt;/script&gt;
  &lt;canvas id="diaryChart" class="diary-chart__chart" width="925" height="161"&gt;&lt;/canvas&gt;</code></pre>
  </div>
  </div>
  </p>