ADDED: Badge about CII Best Practices "Passing" criteria level to README.

Author: balassy

README.md

@@ -15,6 +15,7 @@ This sample uses the [Serverless Application Framework](https://serverless.com/)
 [![DevDependencies](https://david-dm.org/balassy/aws-lambda-typescript/dev-status.svg)](https://david-dm.org/balassy/aws-lambda-typescript#type=dev)
 [![codebeat badge](https://codebeat.co/badges/cd3e0118-3d7f-4c0d-8d27-14d05df5a356)](https://codebeat.co/projects/github-com-balassy-aws-lambda-typescript-master)
 [![Greenkeeper badge](https://badges.greenkeeper.io/balassy/aws-lambda-typescript.svg)](https://greenkeeper.io/)
+[![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/2154/badge)](https://bestpractices.coreinfrastructure.org/projects/2154)
 
 ## Features