title: How do I add a tooltip to the x-axis labels in highcharts?
body: <p>How do I add a tooltip to the x-axis labels in highcharts?</p>
  
  <pre><code>xAxis: {
    categories: ['Apples', 'Oranges', 'Pears', 'Grapes', 'Bananas'],
    labels: {
      x: 5,
      useHTML: true,
      formatter: function () {
        return categoryImgs[this.value];
      }
    }
  }
  </code></pre>
  
  <p>Currently, tooltips are only shown on the points in the chart, I want the user to also see a tooltip/custom description when hovering on the labels on x-axis. Is that possible? Thanks</p>