Update free-programming-interactive-tutorials-en.md

[bikashdaga]

Have added a couple of Scaler Topics popular courses. I believe this will add value to this repo.

[eshellman]

How do we know which of these courses are free? Note that we only list free courses. What is the business model for Scaler? Have you taken a Scaler course? Be sure to check the free-programming-books-lint output for linter errors. Alphabetical order and spacing are the most common problems. (a space comes before any letter) When the course has a named instructor, credit it as Instructor Name (Scaler Topics)

[bikashdaga]

Hi, @eshellman!

I have made the changes - and fixed all the errors.

1. How do we know which of these courses are free? - marked free course
2. What is the business model for Scaler? - In short, Scaler is an online platform that offers tech education and career acceleration programs.
3. Have you taken a Scaler course? - Just started doing [Python Certification Course](https://www.scaler.com/topics/course/python-for-beginners/).

[eshellman]

Thanks, and welcome to free-programming-books!