Leaflet setup

If you are not familiar with Leaflet, make sure to read and follow the installation instructions from its 🍃 quick start guide before using this library.
You will notably need to add its CSS to your page to render the map properly, and set the height of the <Map> container.

All components are React wrappers for Leaflet elements and layers, they need a map instance and therefore must be included in a top-level <Map> component.