add free ebook notification

Author: Packt-ITService

README.md

@@ -62,3 +62,7 @@ find all the instructions you need in the chapter's text.
 **Note**:
 Always remember to activate the virtual environment before you install
 third-party libraries.
+### 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/9781801815093">https://packt.link/free-ebook/9781801815093 </a> </p>