Feature voronoi and EEZ extras

[irm-codebase]

Fixes #51, #54, #50

Summary of changes in this pull request

• Significantly faster processing thanks to per-country parallelisation and smarter overlap identification using shapely STRtree.
• Optional Voronoi splitting for offshore zoning.
• Option to 'append' EEZ codes to countries (helps take care of odd cases, like Alaska and Hawaii for the USA).

Reviewer checklist

• There are no pip dependencies in the module's environment files (workflow/envs/).
• All rules use pathvars (e.g., <results>) in their inputs and outputs.
• The integration test-suite is successful, including:
  • pre-commit.ci tests pass.
  • tests pass for all relevant OS configurations (linux, osx, windows).
• Module documentation is up-to-date, including:
  • INTERFACE.yaml mentions all relevant pathvars and wildcards.
  • README.md describes how to use the module and has the necessary citations.

[sjpfenninger]

This looks good to me. Also, I know it's not part of this PR, but a comment on the README structure: it looks good, though I would add a Quickstart section early on in all module docs, with the idea that this provides one or two quick/easy one-liners to run the workflow without wiring it up as a module. E.g. something like:

## Quickstart

Run this standalone with the configuration in `config/config.yaml` to produce both the parquet output file and a PNG plot of the shapes:

`pixi run snakemake --cores 2 results/shapes.parquet results/shapes.png`