Add a "most popular" maps section

[waldyrious]

Is your feature request related to a problem? Please describe.
I'm slowly discovering what uMap can do, and browsing existing maps is a great way to learn new tricks and possibilities. The search functionality is great, but there's no way to filter for maps that are of high quality and/or popular among the site's users.

Describe the solution you'd like
I'd like there to be a page on the site listing the most popular (e.g. most starred/favorited, most visited, etc.) maps. This would allow people to learn from the best of what can be done with uMap.

Describe alternatives you've considered
A manual selection of featured maps would also work, but it would require continued curation work by the site maintainers, so I believe it would be less desirable for all involved.

[yohanboniface]

We should promote the staring functionality and have a "most starred" maps page.