Issue #3484065 by grimreaper, pdureau: Carousel item: remove active prop,...

Issue #3484065 by grimreaper, pdureau: Carousel item: remove active prop, handle automatically with JS.

Closes #3484065

templates/patterns/carousel/js/carousel.js

+((Drupal, once) => {
+  Drupal.ui_suite_bootstrap_carousel = Drupal.ui_suite_bootstrap_carousel || {};
+
+  /**
+   * Set active class on the first item.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches the behaviors for the active class.
+   */
+  Drupal.behaviors.ui_suite_bootstrap_carousel = {
+    attach(context) {
+      once('carousel-active', '.carousel', context).forEach((carousel) => {
+        const items = carousel.querySelectorAll(
+          '.carousel-inner .carousel-item',
+        );
+        if (items.length === 0) {
+          return;
+        }
+
+        items.item(0).classList.add('active');
+      });
+    },
+  };
+})(Drupal, once);