title: UICollectionView: add spacing between header and items
body: <p>I want to add some spacing between my header and the actual items, which currently look like this:</p>
  
  <p><a href="https://i.stack.imgur.com/32v77.png" rel="noreferrer"><img src="https://i.stack.imgur.com/32v77.png" alt="screenshot1"></a></p>
  
  
  
  <pre><code>func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -&gt; UICollectionReusableView {
      // Create header
      switch kind{
          case UICollectionElementKindSectionHeader:
              let headerView = iconCollectionView.dequeueReusableSupplementaryViewOfKind(kind, withReuseIdentifier: "customIconHeaderView", forIndexPath: indexPath) as! CustonIconHeaderView
              headerView.setUp() //add whatever into the view
              return headerView
          default:
              assert(false, "Unexpected element kind")
      }
  
  }
  </code></pre>