Update test-markdown.md

doc/developer/tests/test-markdown.md

@@ -12,3 +12,14 @@ Paste the following tests into Mattermost to test markdown support.
 ~~This should show strikethrough formatting~~
 **This should be bold**
 ```
+
+Here is how it should render: 
+
+# This should render as Heading 1 font size 
+## This should render as Heading 2 font size 
+### This should render as Heading 3 font size 
+#### This should render as Heading 4 font size 
+##### This should render as Heading 5 font size 
+###### This should render as Heading 6 font size 
+~~This should show strikethrough formatting~~
+**This should be bold**