Added AI course (#9956)

* Update free-courses-en.md

* Update free-courses-en.md

* Update free-courses-en.md

courses/free-courses-en.md

@@ -248,6 +248,7 @@
 * [Introduction to TensorFlow for Artificial Intelligence, Machine Learning, and Deep Learning](https://www.coursera.org/learn/introduction-tensorflow) - DeepLearning.ai (Coursera)
 * [MIT Deep Learning and Artificial Intelligence Lectures](https://deeplearning.mit.edu) - Lex Fridman, et al.
 * [MIT's Artificial Intelligence](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-034-artificial-intelligence-fall-2010/) - Prof. Patrick Henry Winston (MIT OpenCourseWare)
+* [Stanford CS221: Artificial Intelligence: Principles and Techniques \| Autumn 2019](https://www.youtube.com/playlist?list=PLoROMvodv4rO1NB9TD4iUZ3qghGEGtqNX) - Stanford Online
 
 
 ### Assembly