title: Woocommerce filter products by attributes add checkbox
body: <p>I have searched the net and this support forum for the answer but could not get one that is the correct one. WooCommerce default filter product by attribute is working fine, the display types are list and dropdown how can I add a checkbox to the display type. so I can set it to be a dropdown, list or checkbox?</p>
  
  <p>using:
  WooCommerce Version 4.1.0
  Wordpress Version 5.4.1 </p>