add free ebook notification

Author: Packt-ITService

README.md

@@ -110,3 +110,8 @@ $ tox -e ch01
 ### Suggestions and Feedback
 [Click here](https://docs.google.com/forms/d/e/1FAIpQLSe5qwunkGf6PUvzPirPDtuy1Du5Rlzew23UBp2S-P3wB-GcwQ/viewform) if you have any feedback or suggestions.
 
+
+### 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/9781803232577">https://packt.link/free-ebook/9781803232577 </a> </p>