(Changes made) Add Deep Reinforcement Learning Course from Hugging Face (#9760)

* Update free-courses-en.md

* Update free-courses-en.md

Now, in alphabetical order.

courses/free-courses-en.md

@@ -526,6 +526,7 @@
 * [Deep Learning With Tensorflow 2.0 and Keras](https://youtube.com/playlist?list=PLeo1K3hjS3uu7CxAacxVndI4bE_o3BDtO) - codebasics
 * [Deep Multi-Task and Meta Learning](https://cs330.stanford.edu) - Chelsea Finn (Stanford University)
 * [Deep Reinforcement Learning](http://rail.eecs.berkeley.edu/deeprlcourse/) - Sergey Levine
+* [Deep Reinforcement Learning Course - Hugging Face](https://huggingface.co/learn/deep-rl-course/unit0/introduction)
 * [Exploring Fairness in Machine Learning for International Development](https://ocw.mit.edu/resources/res-ec-001-exploring-fairness-in-machine-learning-for-international-development-spring-2020) - Dr. Richard Fletcher, Prof. Daniel Frey, Dr. Mike Teodorescu, Amit Gandhi, Audace Nakeshimana (MIT OpenCourseWare)
 * [Full Stack Computer Vision Tutorial with Tensorflow, Python, Tensorflow.JS with React.JS](https://www.youtube.com/playlist?list=PLgNJO2hghbmhUeJuv7PyVYgzhlgt2TcSr) - Nicholas Renotte
 * [Intro to Deep Learning](https://www.kaggle.com/learn/intro-to-deep-learning) - Ryan Holbrook