Update README.md

Author: schickling

README.md

@@ -116,6 +116,10 @@ yarn add graphql-playground-middleware-lambda
 `handler.js`
 
 ```js
+import lambdaPlayground from 'graphql-playground-middleware-lambda'
+// or using require()
+// const lambdaPlayground = require('graphql-playground-middleware-lambda').default
+
 exports.graphqlHandler = function graphqlHandler(event, context, callback) {
   function callbackFilter(error, output) {
     // eslint-disable-next-line no-param-reassign