title: How update option without reload chart (ng2-chart)
body: <p>I need to update option in the chart and I need to show the chart with  new option.
  I WANT that the chart IS NOT RELOAD
  this is my ts.</p>
  
  <pre><code>   @ViewChild(BaseChartDirective)  chart: any;
  
  lineChartOptions: any = {
      responsive: true,
      zoom:{
        // Boolean to enable zooming
        enabled: false,
        sensitivity: 0.5,
        // Enable drag-to-zoom behavior
        drag: true,
  
        // Zooming directions. Remove the appropriate direction to disable 
        // Eg. 'y' would only allow zooming in the y direction
        mode: 'xy',
        rangeMin: {
          // Format of min zoom range depends on scale type
          x: null,
          y: null
        },
        rangeMax: {
          // Format of max zoom range depends on scale type
          x: null,
          y: null
        }
      }
  </code></pre>
  
  <p>Now when an external event becames and I need to chage option and active zoom:</p>
  
  <pre><code>handleExternalEvent(){
   this.lineChartOptions.zoom.enabled=true;
      this.chart.chart.update();
  }
  </code></pre>
  
  <p>The problem is update doesn't work. If I do "this.chart.refresh()" the new chart with new options it reloaded but, I don't want reload chart. ANyone can help me?</p>