Add links to project structure materials

Author: jerry-git

README.md

@@ -37,5 +37,5 @@ If you can not access Python and/or Jupyter Notebook on your machine, you can st
 1. [Goodies of the Standard Library](http://htmlpreview.github.com/?https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/html/std_lib.html) [[notebook]](https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/std_lib.ipynb)
 1. [Testing with pytest - part 2](http://htmlpreview.github.com/?https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/html/testing2.html) [[notebook]](https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/testing2.ipynb) [[exercise]](https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/exercises/testing2_exercise.ipynb)
 1. [Virtual environment](http://htmlpreview.github.com/?https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/html/venv.html) [[notebook]](https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/venv.ipynb)
-1. Project structure
+1. [Project structure](http://htmlpreview.github.com/?https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/html/project_structure.html) [[notebook]](https://github.com/jerry-git/learn-python3/blob/master/notebooks/beginner/project_structure.ipynb)
 1. Recap exercise 2