title: Make flatpickr input required
body: <p>I'm using the amazing <a href="https://chmln.github.io/flatpickr/" rel="noreferrer">flatpickr</a> on a project and need the calendar date to be mandatory.</p>
  
  <p>I'm trying to have all the validation in native HTML, so I was naively trying with just adding the <code>required</code> attribute to the input tag, but that doesn't appear to be working.</p>
  
  <p>Is there a way of natively making a date mandatory with flatpickr or do I need to write some custom checks?</p>