title: Adding data labels to treemap chart
body: <p>I have a treemap chart which contain age bins (under 18, 18-21 etc) and the number of customers as the size of the treemap's "boxes"
  I want to add the number of customers as data label (e.g., there are 200 customers in the age of 18-21; I want the chart to present 200 as data label)..</p>
  
  <p>How can I do it?</p>
  
  <p>Thank you in advance! </p>