Added Course in free-courses-en.md (#10742)

* Updated free-programming-books-langs.md

* Added a course to free-courses-en.md

* Updated courses/free-courses-en.md

Co-authored-by: Sohan Sai <76840110+sohansai@users.noreply.github.com>

* Updated free-programming-books-langs.md

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Co-authored-by: Sohan Sai <76840110+sohansai@users.noreply.github.com>

courses/free-courses-en.md

@@ -1520,6 +1520,7 @@
 ### Security
 
 * [Computer Systems Security](https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-858-computer-systems-security-fall-2014) - Prof. Nickolai Zeldovich (MIT OpenCourseWare)
+* [Ethical Hacking](https://www.youtube.com/playlist?list=PLDV15dUauYyOcloXu7GXHJ6Xxq5XTBg1k) - Cyber Square
 * [Ethical Hacking](https://www.hacker101.com/videos) - Hacker101
 * [Ethical Hacking - Basics (Kali 2021)](https://www.udemy.com/course/ethical-hacking-basics-kali-20211) - Arthur Salmon (Udemy)
 * [Ethical Hacking - SQL Injection Attack](https://www.udemy.com/course/sql-injection-ethical-hacking) - Sunil K. Gupta, Knowledge Aacademy (Udemy)