Export Change from v2/firestore (#1379)

* export change

* add changelog

Author: colerogers

CHANGELOG.md

@@ -0,0 +1 @@
+- Export Change interface from the v2 firestore path (#1379).

src/v2/providers/firestore.ts

@@ -35,6 +35,8 @@ import {
   createSnapshotFromProtobuf,
 } from "../../common/providers/firestore";
 
+export { Change };
+
 /** @internal */
 export const writtenEventType = "google.cloud.firestore.document.v1.written";