fix(lambda-event-sources): add missing export of streams.ts (#4362)

* fix(lambda-event-sources): add missing export of streams.ts

Fixes #4352

Author: RomainMuller

packages/@aws-cdk/aws-lambda-event-sources/lib/index.ts

@@ -1,6 +1,7 @@
+export * from './api';
 export * from './dynamodb';
 export * from './kinesis';
-export * from './sqs';
 export * from './s3';
 export * from './sns';
-export * from './api';
+export * from './stream';
+export * from './sqs';

packages/@aws-cdk/aws-lambda-event-sources/lib/stream.ts

@@ -2,7 +2,8 @@ import lambda = require('@aws-cdk/aws-lambda');
 import {Duration} from '@aws-cdk/core';
 
 /**
- * @internal
+ * The set of properties for event sources that follow the streaming model,
+ * such as, Dynamo and Kinesis.
  */
 export interface StreamEventSourceProps {
   /**
@@ -32,8 +33,6 @@ export interface StreamEventSourceProps {
 
 /**
  * Use an stream as an event source for AWS Lambda.
- *
- * @internal
  */
 export abstract class StreamEventSource implements lambda.IEventSource {
   protected constructor(protected readonly props: StreamEventSourceProps) {