Update free-courses-en.md (#8234)

Added Docker course by Programming with Mosh

courses/free-courses-en.md

@@ -461,6 +461,7 @@
 
 * [Docker](https://www.youtube.com/playlist?list=PLhW3qG5bs-L99pQsZ74f-LC-tOEsBp2rK) - Raghav Pal
 * [Docker Essentials](https://cognitiveclass.ai/courses/docker-essentials) - CognitiveClass.ai
+* [Docker Tutorial for Beginners](https://www.youtube.com/watch?v=pTFZFxd4hOI) - Programming with Mosh!
 * [Docker Tutorial for Beginners](https://www.youtube.com/playlist?list=PL6gx4Cwl9DGBkvpSIgwchk0glHLz7CQ-7) - Thenewboston
 * [Docker Tutorial for Beginners](https://www.youtube.com/watch?v=fqMOX6JJhGo) - FreeCodeCamp
 * [Docker Tutorial for Beginners \[FULL COURSE in 3 Hours\]](https://www.youtube.com/watch?v=3c-iBn73dDE) - TechWorld with Nana