title: Add a mandatory custom checkbox in WooCommerce checkout only for certain countries (shipping destinations)
body: <p>I would like to add a conditional checkbox to my woocommerce checkout page, similar to the code in this answer:</p>
  <p><a href="https://stackoverflow.com/a/45911284/9184870">https://stackoverflow.com/a/45911284/9184870</a></p>
  <p>But the checkbox should only appear for ceratin countries (shipping destinations)?</p>