Consider adding a field for Fellow project URLs

[matthewfeickert]

We do have github-username, which we present as their GitHub repo on their page. I suppose we can add a field to the project for project-urls. I prefer "project-url" since some people are using gitlab as well as GitHub.

Originally posted by @rct225 in #1616 (comment)

[matthewfeickert]

It seems like this would be useful to have, as interested people probably want to get to the project instead of having to look through slides for links.