gtm soda click checkout (rewrite Dan)

<script>
    (function () {
        function addKeyToStorage() {
  	  		var NATIVE_UPSELL_BUTTON = document.querySelector('[bi-type="upsell go to cart(checkout) pdp"]');
  			if (!NATIVE_UPSELL_BUTTON) {
   				 return;
  			}
  			NATIVE_UPSELL_BUTTON.addEventListener('click', function () {
    			localStorage.setItem('nativeUpsellButtonClicked', window.location.href);
 		 	});
        }
        if (document.readyState === 'loading') {
            document.addEventListener('DOMContentLoaded', addKeyToStorage);
        } else {
            addKeyToStorage();
        }
    })();
</script>