Use vector tiles

[ralienpp]

For lack of a better solution, we switched to self-hosted tiles available on maptiles.railean.net.

To reduce the load on the server and the bandwidth consumed by mobile devices, it is highly desirable to switch to vector tiles. Currently we're using raster tiles, though the backend supports vectors too. It is a matter of figuring out how to do this with React-Leaflet.

[unrevised6419]

For rendering vector tiles, more work needs to be done

• https://eox.at/2020/01/vector-tiles-with-dynamically-updated-style-in-leaflet-lpvis/
• https://github.com/Leaflet/Leaflet.VectorGrid
• https://github.com/maplibre/maplibre-gl-js