title: ESLint prefer-arrow-callback on array.map
body: <pre><code>import React from 'react';
  
  export default class UIColours extends React.Component {
    displayName = 'UIColours'
  
    render() {
      const colours = ['black', 'red', 'white', 'orange', 'green', 'yellow', 'blue', 'darkblue', 'lilac', 'purple', 'darkPurple'];
      return (
        &lt;div className="ui-colours-container row bg-white"&gt;
          &lt;div className="col-md-16 col-xs-16 light"&gt;
            &lt;div className="color-swatches"&gt;
              {colours.map(function(colour, key) {
                return (
                  &lt;div key={key} className={'strong color-swatch bg-' + colour}&gt;
                    &lt;p&gt;{colour}&lt;/p&gt;
                  &lt;/div&gt;
                );
              })}
            &lt;/div&gt;
          &lt;/div&gt;
        &lt;/div&gt;
     );
    }
  }
  </code></pre>
  
  <blockquote>
    <p>12:26  error    Unexpected function expression                  prefer-arrow-callback</p>
  </blockquote>
  
  <p>I've looked at the map documentation and can't find a good example of multiple parameters.</p>