Add new site to Coding Practice Sites

Author: jackieoft

README.md

@@ -259,4 +259,5 @@ But knowing the stuff will help you become better! :muscle:*
 - :link: [At Coder](https://atcoder.jp/)
 - :link: [Codility](https://www.codility.com/)
 - :link: [ICPC Problem Archive](https://icpc.kattis.com/)
-- :link: [Codemia](https://codemia.io/)
+- :link: [Codemia](https://codemia.io/)/)
+- :link: [LabEx](https://labex.io/)