title: print key of highest value in map
body: <p>I have created the following map:</p>
  
  <pre><code>(function getLakes() {
      let lakes = new Map ([['Caspian Sea', 560], ['Tarn Hows', 53], ['Crater Lake', 324], ['Lake Tanganyika', 803], ['Lake Vostok', 546],
      ['Lake Baikal', 897]]);
      let fathom = 1.829;
  
      console.log("The deepest lake is " +  Math.max(...lakes.values())*fathom);
      })();
  </code></pre>
  
  <p>Additionally to logging the value, I would also like to log the key, so that I end up with the following, additional line:
  "The deepest lake is Lake Baikal."</p>
  
  <p>I am not sure how to make this work - does anyone have an idea? </p>
  
  <p>Thank you!</p>