feat: Add a place for ppl to add the projects they've created

[BekahHW]

In the Intro course, we have a way for contribs to add themselves. It'd be nice to do something here. Maybe they can add their project to a page or the readme

[adiati98]

I'd say adding a new page would be better than to the README so that it don't get clutter.

As we do in intro course, we have guestbook repo to add themselves, and not to the intro's README.