Refactor LPSortableInstances to use Map() and Set()

js/builder.js

@@ -417,17 +417,15 @@
    * API for adding Layout Paragraphs Sortable.js instances.
    */
   Drupal.LPSortableInstances = {
-    intances: {},
+    instances: new Map(),
     add: function (id, instance) {
-      if (this.intances[id]) {
-        this.intances[id].push(instance);
-      }
-      else {
-        this.intances[id] = [instance];
+      if (!this.instances.has(id)) {
+        this.instances.set(id, new Set());
       }
+      this.instances.get(id).add(instance);
     },
     get: function (id) {
-      return this.intances[id] || [];
+      return this.instances.get(id) || new Set();
     }
   };