Add interactive tutorial page in German and Python course - changes made (EbookFoundation#9668)

* Create free-programming-interactive-tutorials-de.md

docs: Add interactive tutorials in German

Create a page for interactive tutorials in German because it does not exist yet.
Add a free interactive Python tutorial in German. It is stated on the linked website that it is free and usabale without registration.

* Update README.md

* Add German interactive tutorial page link to README.md

Author: skaspy

README.md

@@ -167,6 +167,7 @@ This project lists books and other resources grouped by genres:
 
 + [Chinese / 中文](more/free-programming-interactive-tutorials-zh.md)
 + [English](more/free-programming-interactive-tutorials-en.md)
++ [German](more/free-programming-interactive-tutorials-de.md)
 + [Japanese / 日本語](more/free-programming-interactive-tutorials-ja.md)
 + [Portuguese (Brazil)](more/free-programming-interactive-tutorials-pt_BR.md)
 + [Russian / Русский язык](more/free-programming-interactive-tutorials-ru.md)

more/free-programming-interactive-tutorials-de.md

@@ -0,0 +1,8 @@
+### Index
+
+* [Python](#python)
+
+
+### Python
+
+* [CS Circles - Interaktiv Python lernen!](https://cscircles.cemc.uwaterloo.ca/de/) - University of Waterloo & Bundesweite Informatikwettbewerbe (HTML)