Added Django Girls Extensions

Author: sayands

README.md

@@ -162,6 +162,7 @@ To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIB
 
 * [Build a Microblog with Flask](https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world)
 * [Create a blog webapp in Django](https://tutorial.djangogirls.org/en/)
+* [Extend the Django Blog Web App](https://legacy.gitbook.com/book/djangogirls/django-girls-tutorial-extensions/details)
 * [Choose Your Own Adventure Presentations](https://www.twilio.com/blog/2015/03/choose-your-own-adventures-presentations-wizard-mode-part-1-of-3.html)
 * [Build a Todo List with Flask and RethinkDB](https://realpython.com/blog/python/rethink-flask-a-simple-todo-list-powered-by-flask-and-rethinkdb/)
 * [Build a Todo List with Django and Test-Driven Development](http://www.obeythetestinggoat.com/)