Move the Item data models into their own folder for better organization

module/models/Item/DescribedItemData.mjs

@@ -0,0 +1,14 @@
+import { CommonItemData } from "./CommonItemData.mjs";
+
+export class DescribedItemData extends CommonItemData {
+	static defineSchema() {
+		const fields = foundry.data.fields;
+		return mergeObject(super.defineSchema(), {
+			description: new fields.StringField({
+				initial: ``,
+				blank: true,
+				trim: true,
+			}),
+		});
+	};
+};