title: TypeError: Highcharts.mapChart is not a function
body: <p>I am trying to plot a highmap in react using typescript. I have additionally loaded the highcharts types which include highmaps.</p>
  
  <pre><code>class InvestmentChart extends React.Component {
    componentDidMount() {
      Highcharts.mapChart("investment", {
        chart: {
  ...
  </code></pre>
  
  <p>Cheers</p>
  
  <p>See live <a href="https://codesandbox.io/s/nkrww6ly3l" rel="nofollow noreferrer">here</a>.</p>