update free-programming-books.md (#4379)

* update free-programming-books.md

added Playtime with Hyperledger Composer book.

* update

free-programming-books.md

@@ -641,6 +641,7 @@
 * [Packt Publishing: A free book every day](https://www.packtpub.com/packt/offers/free-learning) (PDF, ePub, Mobi, Kindle) *(account required)*
 * [PDQ: Pretty Darn Quick: An Agile, All-Purpose Methodology](https://leanpub.com/PDQ) - Jeff Franz-Lien  *(Leanpub account or valid email requested)*
 * [Philosophy of Computer Science](http://www.cse.buffalo.edu/~rapaport/Papers/phics.pdf) (PDF)
+* [Playtime with Hyperledger Composer](https://schadokar.dev/ebooks/playtime-with-hyperledger-composer/) - Shubham Chadokar (PDF)
 * [PNG: The Definitive Guide](http://www.libpng.org/pub/png/book/)
 * [Pointers And Memory](http://cslibrary.stanford.edu/102/PointersAndMemory.pdf) (PDF)
 * [Principles of Computer System Design](http://ocw.mit.edu/resources/res-6-004-principles-of-computer-system-design-an-introduction-spring-2009/online-textbook/part_ii_open_5_0.pdf) (PDF)