title: Add date-picker to slack dialog?
body: <p>I want to add date-picker elements to slack dialog. It is clear that from 
  <a href="https://api.slack.com/dialogs#elements" rel="nofollow noreferrer">documentation</a>, we can only add input, text-area, and select elements.</p>
  
  <p>Is there any hack to use date-picker in the slack dialog?</p>