Add Docker Tutorials (#3994)

Co-authored-by: Nkonbo <konbo666@tutanota.com>

free-courses-en.md

@@ -14,6 +14,7 @@
 * [Data Science](#data-science)
 * [Databases](#databases)
 * [Deep Learning](#deep-learning)
+* [Docker](#docker)
 * [Game Development](#game-development)
 * [Git](#git)
 * [Go](#go)
@@ -178,6 +179,12 @@
 * [What is Deep Learning](https://www.udacity.com/course/deep-learning--ud730) (Udacity)
 
 
+### Docker
+
+* [Docker Tutorial](https://www.tutorialspoint.com/docker/index.htm) - TutorialsPoint
+* [Docker Tutorial for Beginners](https://www.youtube.com/watch?v=fqMOX6JJhGo) - FreeCodeCamp
+
+
 ### Game Development
 
 * [Unity Beginner Fundamentals](https://learn.unity.com/course/unity-beginner-fundamentals)(Unity Learn)