title: Flow layout with centered content
body: <p>I have a row with items which should stack when the window width gets too small for displaying all items in a row, as shown in the following sketch:</p>
  
  <p><a href="https://i.stack.imgur.com/00A6Z.png" rel="noreferrer"><img src="https://i.stack.imgur.com/00A6Z.png" alt="enter image description here"></a></p>
  
  <p>The <code>Flow</code> component stacks the items but they are not centered but aligned on the left or right side:</p>
  
  <pre><code>Flow {
      Item {}
      Item {}
      Item {}
      Item {}
      Item {}
  }
  </code></pre>
  
  <p>Is there a built-in way in QML to make the flow centered?</p>