Adding bounding-box attribute

[JoOkuma]

This is an intermediate PR to include bounding boxes before the major refactoring of #119

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 88.20%. Comparing base (be07bce) to head (9e98a44).

Files with missing lines	Patch %	Lines
src/tracksdata/nodes/_regionprops.py	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #121      +/-   ##
==========================================
+ Coverage   88.18%   88.20%   +0.01%     
==========================================
  Files          47       47              
  Lines        2794     2797       +3     
  Branches      459      460       +1     
==========================================
+ Hits         2464     2467       +3     
  Misses        197      197              
  Partials      133      133              

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