Create minimal example for disaggregation and aggregation function

[jnnr]

The example can be found here (work in progress) https://github.com/jnnr/spatial-disaggregation

[jnnr]

As part of the preprocessing, we aim to disaggregate all spatial subnational input data. The data should be prepared in raster format, which can later be aggregated to any custom spatial resolution. In a minimal example, we aim to implement several functions which can in the next step be applied everywhere in Euro-Calliope where subnational spatial data is preprocessed.

The functions may be called

• disaggregate_polygon_to_raster
• aggregate_polygon_to_raster

The example can adapt the regionalisation in scripts/heat/rescale.py