Fix pushPayload types

Author: wagenet

packages/legacy-compat/src/index.ts

@@ -255,7 +255,9 @@ export function normalize(this: Store, modelName: string, payload: ObjectValue)
     @param {Object} inputPayload
   */
 // TODO @runspired @deprecate pushPayload in favor of looking up the serializer
-export function pushPayload(this: Store, modelName: string, inputPayload: ObjectValue): void {
+export function pushPayload(this: Store, inputPayload: ObjectValue): void;
+export function pushPayload(this: Store, modelName: string, inputPayload: ObjectValue): void;
+export function pushPayload(this: Store, modelNameOrPayload: string | ObjectValue, inputPayload?: ObjectValue): void {
   upgradeStore(this);
   assert(
     `Attempted to call store.pushPayload(), but the store instance has already been destroyed.`,