title: GridView rows outer margin
body: <p>I cannot find out a way to add an outer margin to the GridView rows. I found the <code>setHorizontalSpacing</code> and <code>setVerticalSpacing</code> properties which add inner padding between the GridView rows, however it doesn't apply to the outer borders of the rows.</p>
  
  <p>I'd like to have a result as it's featured on the Google Play store:</p>
  
  <p><img src="https://i.stack.imgur.com/45VZI.png" alt="enter image description here"></p>
  
  <p>Thanks!</p>