title: How to show data labels in charts created via Openpyxl
body: <p>I am creating charts using openpyxl with the following code.
  By default it doesn't show data labels - so I have to right-click the chart and choose 'Add Data Labels" manually. How do I do that with Openpyxl command?
  Thanks in advance !</p>
  
  <pre><code>data = Reference(ws, min_col=2, min_row=1, max_col=6, max_row=10)
  titles = Reference(ws, min_col=1, min_row=2, max_row=10)
  chart = BarChart3D()
  chart.add_data(data=data, titles_from_data=True)
  chart.set_categories(titles)
  ws.add_chart(chart, "C10")
  </code></pre>