Art pages now show top contributors

Each snapshot now shows the top contributors. To keep this display uncluttered, we’re only showing the top 5 contributors.

This doesn’t mean that they’ve done a lot of the work - sometimes there are only 3 contributors, and one person has moved 998 tiles, and the other two just one tile.

It’s a simple algorithm for sure, but using a cutoff value for when NOT to list someone as contributor didn’t seem fair - so we simply show the top 5 contributors, ordered by the number of tiles moved.