explain how to use hillshades and terrain tiles to use in maplibre-gl

[janstuemmel]

fyi: there's an old PR that i learned basic things: versatiles-org/versatiles-style@main...refs/heads/hillshade-vectors#diff-5fbf2f924e8dd105c6fb171fd70656c6fd948b86a2f6b6aa9ecdd25e5a6b4e42L48

[yetzt]

i've added tilesets to our documentation, including some basic map style examples: https://docs.versatiles.org/basics/tilesets.html

in short: as of now you need to add them as sources and layers to your map style, wither directly by editing the style json, or using an edito like maputnik.

for the future we are planning to integrate the different available layers to our style generator.