feat(books): How To Code in Node.js - eBook (#5977)

* feat(books): How To Code in Node.js eBook

Authors: David Landup and Marcus Sanatan
Editors: Timothy Nolan and Brian MacDonald
Publisher: Stack Abuse @StackAbuse, Digital Ocean
Date: 2020-12

PDF: https://assets.digitalocean.com/books/how-to-code-in-nodejs.pdf
EPUB: https://assets.digitalocean.com/books/how-to-code-in-nodejs.epub

* fix(books): sync format with their tutorial

books/free-programming-books-langs.md

@@ -1214,6 +1214,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 
 * [An Introduction to libuv](https://nikhilm.github.io/uvbook/) - Nikhil Marathe  ([PDF](http://nikhilm.github.io/uvbook/An%20Introduction%20to%20libuv.pdf) - [ePub](http://nikhilm.github.io/uvbook/An%20Introduction%20to%20libuv.epub))
 * [Full Stack JavaScript: Learn Backbone.js, Node.js and MongoDB](https://github.com/azat-co/fullstack-javascript) - Azat Mardan
+* [How To Code in Node.js - eBook](https://www.digitalocean.com/community/books/how-to-code-in-node-js-ebook) - David Landup, Marcus Sanatan @ Stack Abuse, Digital Ocean (PDF, EPUB)
 * [Introduction to Node.js](https://nodejs.dev/learn) (HTML)
 * [Mixu's Node Book](http://book.mixu.net/node/)
 * [Module Patterns](https://leanpub.com/modulepatterns) - Pedro Teixeira (HTML, PDF, EPUB, Kindle) *(Leanpub account or valid email requested)*