Support Markdown Content in Nested Menu Index Files

[allocgator]

Feature Request:

Nested menus like Guides, Reference, etc. only show the title and description from the _index.md markdown file.

Formatting directives like headings, text, URLs, etc. are ignored.

Take the Guides nested menu for instance - an introduction on whats going to be covered, followed by the links to "Features", "Theme Options", and "Shortcodes" would give the reader a bigger picture and a better understanding.

It's better than simply listing the links IMO.

[colinwilson]

I prefer (for now) to keep the nested menu pages clean and concise, and rely on the description from _index.md and the description from the card links on the page to guide visitors.

That being said, I agree that this should be an option for theme users. Will definitely update the list template to accommodate Markdown content.

Thanks 👍