Debut theme (Slate) changes to support bundle availability check

bundled.liquid

// theme.liquid
  <script>
  window.addEventListener("load", function(event) {
    $('.single-option-selector').trigger('change'); // trigger bundle check on initial variant
  });
  </script>

// theme.js - line 2438
    _updateAddToCart: function(evt) {
      var variant = evt.variant;

      if (variant) {
        $(this.selectors.productPrices)
          .removeClass('visibility-hidden')
          .attr('aria-hidden', 'true');
        
        var _this = this,
            quantityField = $('input[name=quantity]');

        bundled(variant, function(bundle) {
          if (variant.available && bundle.available) {
            $(_this.selectors.addToCart).prop('disabled', false);
            $(_this.selectors.addToCartText).text(theme.strings.addToCart);
            quantityField.attr('max', bundle.quantity);
            quantityField.val(Math.min(bundle.quantity, quantityField.val()));
          } else {
            // The variant doesn't exist, disable submit button and change the text.
            // This may be an error or notice that a specific variant is not available.
            $(_this.selectors.addToCart).prop('disabled', true);
            $(_this.selectors.addToCartText).text(theme.strings.soldOut);
          }
        });
      } else {
        $(this.selectors.addToCart).prop('disabled', true);
        $(this.selectors.addToCartText).text(theme.strings.unavailable);
        $(this.selectors.productPrices)
          .addClass('visibility-hidden')
          .attr('aria-hidden', 'false');
      }
    },