add free ebook notification

README.md

@@ -55,3 +55,7 @@ Prabhu has worked with Hewlett Packard and has deep experience in software engin
 Prabhu is passionate about Rust and blockchain and specializes in distributed systems. He considers coding to be a creative craft, and an excellent tool to create new digital worlds (and experiences) sustained through rigorous software engineering.
 
 
+### Download a free PDF
+
+ <i>If you have already purchased a print or Kindle version of this book, you can get a DRM-free PDF version at no cost.<br>Simply click on the link to claim your free PDF.</i>
+<p align="center"> <a href="https://packt.link/free-ebook/9781800560963">https://packt.link/free-ebook/9781800560963 </a> </p>