fix typo in readme

Author: bjhogan

Serverless/EventBridgeLambdaAndS3Example/Readme.md

@@ -1,5 +1,5 @@
 # Event-driven .NET applications with AWS Lambda and Amazon EventBridge
 
-This is a companion project to a forthcoming blog post on using Amazon EventBridge with AWS Lambda function. 
+This is a companion project to a forthcoming blog post on using Amazon EventBridge with an AWS Lambda function. 
 
 This readme will be updated to link to the blog post soon.