Update CONTRIBUTING.md

Co-Authored-By: hpdang <[email protected]>

Author: perploug

CONTRIBUTING.md

@@ -84,7 +84,7 @@ The `-s` in the above commit message signs your commit.
 ## Submit a blog article to [Zalando Open Source Blog](https://opensource.zalando.com/blog/)
 The blog is built with [Github Pages](https://help.github.com/articles/what-is-github-pages/). Please set up a local version of your [Jekyll GitHub Pages site](https://help.github.com/articles/setting-up-your-github-pages-site-locally-with-jekyll/) to test changes locally before making a pull request
 - Blog articles are stored in folder **/_posts/**
-- To create a new article, create a .md file with [markdown](https://en.wikipedia.org/wiki/Markdown)
+- To create a new article, create a .md file with [markdown](https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet)
 - Each blog article requires a banner image which is stored in folder **/assets/img/banners/**. You can add a new banner there or use one of the exisiting ones. 
 - If you include images in the content of the article, please add those into the folder **/assets/img/**. 
 - Please do not forget to test your changes locally before submitting a pull request.