Finish the Pet data model

module/models/Item/Pet.mjs

@@ -0,0 +1,12 @@
+import { DescribedItemData } from "./DescribedItemData.mjs";
+
+export class PetItemData extends DescribedItemData {
+	static defineSchema() {
+		const fields = foundry.data.fields;
+		return mergeObject(super.defineSchema(), {
+			purchase: new fields.NumberField({ initial: 0, }),
+			upkeep: new fields.NumberField({ intial: null, nullable: true }),
+			pokeballd: new fields.BooleanField({ initial: false }),
+		});
+	};
+};