feat: re-export GoogleAuth and AuthClient from google-auth-library (fixes #555)

Author: kgala2

src/index.ts

@@ -29,3 +29,4 @@ export {
 };
 export {IpAddressTypes};
 export {AuthTypes};
+export {GoogleAuth, AuthClient} from 'google-auth-library';

test/exports.test.ts

@@ -0,0 +1,27 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import t from 'tap';
+import {GoogleAuth, AuthClient} from '../src/index';
+
+t.test('should export GoogleAuth and AuthClient', t => {
+  t.ok(GoogleAuth, 'GoogleAuth should be exported');
+  t.ok(AuthClient, 'AuthClient should be exported');
+  t.equal(
+    typeof GoogleAuth,
+    'function',
+    'GoogleAuth should be a constructor function'
+  );
+  t.end();
+});