Update Simple Worldbuilding for Foundry 0.8.x Compatibility

module/item.js

@@ -0,0 +1,22 @@
+import {EntitySheetHelper} from "./helper.js";
+
+/**
+ * Extend the base Item document to support attributes and groups with a custom template creation dialog.
+ * @extends {Item}
+ */
+export class SimpleItem extends Item {
+
+  /** @inheritdoc */
+  prepareDerivedData() {
+    super.prepareDerivedData();
+    this.data.data.groups = this.data.data.groups || {};
+    this.data.data.attributes = this.data.data.attributes || {};
+  }
+
+  /* -------------------------------------------- */
+
+  /** @override */
+  static async createDialog(data={}, options={}) {
+    return EntitySheetHelper.createDialog.call(this, data, options);
+  }
+}