Add a map to show player positions

[Istador]

It would be nice if the players dialog would show the in-game map with the positions of the players.

The data is available via the JSON API and is already passed to the browser from https://api.smoo.it/ so the only thing missing is using that that data in the website software.

Leaflet is very likely the library to use. I already have experience from the Pine Interactive Map, and the prototype map from speyejack also uses Leaflet.

The main thing missing currently is the map graphics. For copyright reasons the maps from the game should not be used. Instead what is needed are royalty-free open maps, preferable as scalable vector graphics (SVG).

The in-game coordinates should not be calculated into map / image coordinates. Instead the Leaflet coordinate system should equal the in-game coordinate system. The map images need to be mapped/transformed to the in-game coordinate system.