Added Mandy.

[ghost]

I added Mandy, another static-site generator written in Rust. I created her. 🙈

[palfrey]

We've recently made a change to the rules regarding additions of new projects, and in order to attempt to be as fair as we can with the process we're now using external popularity metrics to guide this. Our current standards are at least one of: a minimum of 50 stars on Github; 2000 downloads for projects with published crates; or equivalent values in other areas (e.g. downloads in other places, star-type popularity in other repositories).

Unfortunately the project you've submitted doesn't reach any of these thresholds. If you think that we've miscounted or there is another public metric that you think we should take into account, then please re-open this PR and detail where else we should be looking.