Feature Request: Link the markdown preview tool somewhere in the website itself

[MaoShizhong]

Checks

• I have thoroughly read and understand The Odin Project Contributing Guide
• The title of this issue follows the Feature Request: brief description of feature request format, e.g. Feature Request: Add a dark mode to the website
• Would you like to work on this issue?

Description of the Feature Request

There's definitely a small chance I've gone crazy and someone will go "it's right there though", but I've not been able to find anywhere on the website that navigates to the markdown preview tool.

You can of course access it via the URL and bookmark it (and it's linked in the curriculum repo PR template), but I believe that if we have a page that we'd reasonably expect some of the public to need to access, we should make it navigable to from somewhere within the site.

I had thought https://www.theodinproject.com/contributing would be best (accessed via the footer), but given the page contents and structure, I'm not 100% sure where best to put such a link, or whether there's perhaps a better alternative (e.g. as a distinct footer list item, or in the header nav etc.).

Acceptance criteria

• Put a link somewhere in the website that takes you to the markdown preview tool.
• Link must be located somewhere that can be reached in some way no matter where you are in the site.

Additional Comments

No response