title: How can I calculate the dimensions of the current region in react-native-maps?
body: <pre><code>latitude: 38.69444432847513
  latitudeDelta: 0.1288559458782288
  longitude: -90.5969550254043
  longitudeDelta: 0.1638044205986091
  </code></pre>
  
  <p>Suppose my map region has the data above (I use onRegionChange)</p>
  
  <p>How can I get the distance (diameter) of the current region, in kilometers?  (the width will be smaller than the height, because the phone is in portrait mode)</p>
  
  <p>Is there an easy conversion I can do?</p>