3D Extrusion of Buildings

[Drabble]

This is a simple implementation for showcasing 3d possibilities in Maplibre-rs.

We simply take the elements in the buildings layer and extrude them with a fixed height.

In the future, it would be very interesting to add details to the buildings that are extruded and extrude based on the height metadata available in OSM.

Extrusion can be enabled/disabled in the Style configuration.

Finally I probably should split the function in tile_pipelines.rs into smaller functions to make it easier to understand.