Update the README.md file

Author: lpozo

pyqt-calculator-tutorial/README.md

@@ -1,4 +1,10 @@
 # Python and PyQt: Building a GUI Desktop Calculator
 
-This folder provides the code examples for the article [Python and PyQt: Building a GUI Desktop Calculator
-](https://realpython.com/python-and-pyqt-building-a-gui-desktop-calculator/).
+This folder provides the code examples for the article [Python and PyQt: Building a GUI Desktop Calculator](https://realpython.com/python-and-pyqt-building-a-gui-desktop-calculator/).
+
+## Folder Content
+
+The current folder `pyqt-calculator-tutorial/` hosts two subfolders:
+
+1. `examples/` contains the source file of every example in the tutorial.
+2. `pycalc/` stores the code and related resources for your PyQt Calculator app.