title: WooCommerce Custom Checkbox Checked by default
body: <p>I am trying to 'check' a checkbox by default in the WooCommerce checkout page.
  I'm using the official WooCommerce Checkout Field Editor plugin to add a checkbox but it doesn't give me the ability to have the checkbox 'checked' by default.</p>
  
  <p>I've tried using this code but it's not working:</p>
  
  <pre><code>function custom_override_checkout_fields ( $fields ) {
      $fields['additional']['uncheck-to-opt-out-of-our-quarterly-newsletter-neuroscience-matters_field']['default'] = 1;
      return $fields;
  } 
  
  add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );
  </code></pre>
  
  <p>Any help would be greatly appreciated. Thanks</p>