add_action('wp_footer', function() {
?>
<script>
document.addEventListener('DOMContentLoaded', function() {
  document.querySelectorAll('.widget_tag_cloud .widget-title').forEach(function(title) {
    title.addEventListener('click', function() {
      this.closest('.widget_tag_cloud').classList.toggle('open');
    });
  });
});
</script>
<?php
});