Added MailChimp Integration Tutorial

Author: sayands

README.md

@@ -130,6 +130,7 @@ To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIB
   * [Part 1](https://scotch.io/tutorials/build-a-serverless-mern-story-app-with-webtask-io-zero-to-deploy-1)
   * [Part 2](https://scotch.io/tutorials/build-a-serverless-mern-story-app-with-webtask-io-zero-to-deploy-2)
 * [Build A Simple Medium Clone using React.js and Node.js](https://codeburst.io/build-simple-medium-com-on-node-js-and-react-js-a278c5192f47)
+* [Integrate MailChimp in JS](https://medium.freecodecamp.org/how-to-integrate-mailchimp-in-a-javascript-web-app-2a889fb43f6f)
 
 #### Angular: