Add shapefile plotting utility function

[BSchilperoort]

Closes #484

Would still be nice to add to user docs somewhere.

[codecov]

Codecov Report

❌ Patch coverage is 82.05128% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.53%. Comparing base (ce00996) to head (97d5601).

Files with missing lines	Patch %	Lines
src/ewatercycle/util.py	82.05%	2 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #485      +/-   ##
==========================================
+ Coverage   78.49%   78.53%   +0.03%     
==========================================
  Files          28       28              
  Lines        1888     1924      +36     
  Branches      162      171       +9     
==========================================
+ Hits         1482     1511      +29     
- Misses        347      349       +2     
- Partials       59       64       +5     

Files with missing lines	Coverage Δ
src/ewatercycle/util.py	84.43% <82.05%> (-0.85%)	⬇️

... and 1 file with indirect coverage changes

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[BSchilperoort]

plot will look like this