Added CodeWars

Author: mr-mig

README.md

@@ -161,3 +161,4 @@ But knowing the stuff will help you become better! :muscle:*
 - :link: [TopCoder](https://www.topcoder.com/)
 - :link: [Exercism](http://www.exercism.io/)
 - :link: [CodeFights](https://codefights.com/)
+- :link: [CodeWars](https://www.codewars.com/)