Added note for documentation style. (#6229)

* Added note for documentation style.

* Added {: .note}

docs/home/contribute/style-guide.md

@@ -15,6 +15,9 @@ docs, follow the instructions on
 
 {% capture body %}
 
+**Note:** Kubernetes documentation uses [GitHub Flavored Markdown](https://github.github.com/gfm/).
+{: .note}
+
 ## Documentation formatting standards
 
 ### Use camel case for API objects