How to add markdown syntaxed description for an to be published in zendesk marketplace

I am looking forward to publish an app in the Zendesk's marketplace by following the documentation and guidelines.

I need some support to clarify the adding of app details like 

• Short description,
• Long description,
• Installation instructions using markdown formatter and placing in the en.json file inside the translations folder.

But when I try to test the same content in the online markdown previewer I can't able to preview it as expected.

Can someone help me with this issue