Add Git concepts learning based tutorial (#7927)

Author: rajenderK7

more/free-programming-interactive-tutorials-en.md

@@ -136,6 +136,7 @@
 * [Git Tutorial](https://www.w3schools.com/git/) - W3Schools
 * [Githug](https://github.com/Gazler/githug) (Tutorial in shell)
 * [Learn Git Branching](https://learngitbranching.js.org)
+* [Learn git concepts, not commands](https://dev.to/unseenwizzard/learn-git-concepts-not-commands-4gjc) - Nico Riedmann, Dev.to
 * [Learn Git with Bitbucket Cloud](https://www.atlassian.com/git/tutorials/learn-git-with-bitbucket-cloud)
 * [Try Git](http://try.github.io)
 * [Visualizing Git Concepts with D3](http://onlywei.github.io/explain-git-with-d3) - Wei Wang