title: Ng2-Charts in Angular: Is 'Auto' supported for display property of Axes
body: <p>I am using ng2-charts and chart.js in Angular, specifically line chart. I am setting the chart options as below</p>
  
  <p>I am setting display property to auto, so that the y-axis is shown only when data mapping to that axis is rendered.
  However, when compiling the angular app I am getting an error </p>
  
  <p>error TS2322: Type 'string' is not assignable to type 'boolean'.</p>
  
  <p>I checked chart.js documentation and it says the display property can be boolean or string and 'Auto' is an accepted value.</p>
  
  <p>Why would I be getting compile error if chart.js supports string for display property?</p>
  
  <pre><code>import {ChartDataSets, ChartData, ChartOptions} from 'chart.js';
  import {Color, BaseChartDirective, Label} from 'ng2-charts';
  </code></pre>
  
  <p>....</p>
  
  <pre><code>private lineChartOptions : (ChartOptions) = {
      responsive: true,
      scales:{
        xAxes: [{
          id: 'x-axis-0',
          position: 'bottom'
        }],
        yAxes: [
          {
            id: 'y-axis-0',
            display: 'auto',
            position: 'left'
          },
          {
            id: 'y-axis-1',
            display: 'auto',
            position: 'right',
            gridLines: {
              color: 'rgba(255,0,0,0.3)',
            },
            ticks: {
              fontColor: 'red',
            }
          },        
        ]
      }
    }
  </code></pre>