title: How to type antd form validateFields' callback parameter
body: <p>As the question title said: how to type the form.validateFields callback parameters when using Form HOC in Ant Design?</p>
  
  <pre><code>// App.tsx
  import { FormComponentProps } from 'antd/lib/form';
  
  interface IProps extends FormComponentProps { ... }
  
  class App extends React.Component&lt;IProps&gt; {
    ...
    handleSubmit = () =&gt; {
      const { form } = this.props
      // the `err` and `values` has `any` type
      // how can I type them, or at least type values?
      form.validateFields((err, values) =&gt; { ... }))
    }
    ...
  }
  
  export default Form.create&lt;IProps&gt;()(App);
  </code></pre>