Merge pull request #1373 from murgatroid99/grpc-js_callback_type_name_2

grpc-js: Make request callback type match the other library

Author: murgatroid99

packages/grpc-js/src/index.ts

@@ -33,6 +33,7 @@ import {
   Client,
   CallInvocationTransformer,
   CallProperties,
+  UnaryCallback
 } from './client';
 import { LogVerbosity, Status } from './constants';
 import * as logging from './logging';
@@ -209,6 +210,7 @@ export {
   CallInvocationTransformer,
   ChannelImplementation as Channel,
   Channel as ChannelInterface,
+  UnaryCallback as requestCallback
 };
 
 /**