Add subtitle for markdown on edit of engines

[natdink]

Can we add a subtitle before the markdown area that says "Add details as markdown"

In the example, we're just using it to store metadata in json format but presumably it would be more useful in nice markdown which not all users might understand from the drop.

Also, markdown appears under the "details" tab which is under description and tag technically. Consider ordering based on how user can expect to see the information on the page.

• Reorganize the modal to be Description first then mardown and other tagging metakeys
• Add the description placeholder text into the description component as a placeholder (this should signal to user that we have generated some random text but it's not actually relevant to their engine)
• Add a subheader before the markdown section that reads "Add details as Markdown" - Can we hyperlink markdown to a public site that tells someone what it is/how to use it?