Update README. to add sync engine blog post

Author: cristiano-belloni

README.md

@@ -449,6 +449,7 @@ It's a great way to learn.
 * [**Node.js**: _Building A Simple Single Sign On(SSO) Server And Solution From Scratch In Node.js._](https://codeburst.io/building-a-simple-single-sign-on-sso-server-and-solution-from-scratch-in-node-js-ea6ee5fdf340)
 * [**Node.js**: _How to create a real-world Node CLI app with Node_](https://medium.freecodecamp.org/how-to-create-a-real-world-node-cli-app-with-node-391b727bbed3)
 * [**Node.js**: _Build a DNS Server in Node.js_](https://engineerhead.github.io/dns-server/)
+* [**Node.js**: _Build a Synchronization Engine with Node.js_and Y.js](https://greenvitriol.com/posts/sync-engine-for-everyone)
 * [**PHP**: _Write your own MVC from scratch in PHP_ ](https://chaitya62.github.io/2018/04/29/Writing-your-own-MVC-from-Scratch-in-PHP.html)
 * [**PHP**: _Make your own blog_](https://ilovephp.jondh.me.uk/en/tutorial/make-your-own-blog)
 * [**PHP**: _Modern PHP Without a Framework_](https://kevinsmith.io/modern-php-without-a-framework)