DOC: add building footprint example notebook

[lisawink]

This PR contains:

• ci/313-latest.yaml
  • new environment file with python 3.13
• datasets/buildings_berlin.parquet
  • example dataset sourced from OSM of central Berlin
• notebooks/building_footprints/building_footprints_example.ipynb (not complete)
  • notebook containing preprocessing steps using the Berlin example data

The last section of the example notebook needs checking (by @martinfleis). I am not sure if snapping is working as expected because before and after snapping is done, the snapping algorithm identifies the same pairs to snap, where I would expect it to no longer identify them.

[martinfleis]

Snapping is a bit broken it seems. Both detection of what should be snapped and the _snap itself. We now get polygons that meet at a corner marked as to be snapped which is not correct in most places. And _snap does not always produce rook contiguity. Needs to be fixed...

[martinfleis]

We now get polygons that meet at a corner marked as to be snapped which is not correct in most places.

This is true but the snapping in these locations is a void operation, so this is fine.