Improve type hints for SpatialGraph

[tlambert03]

alternative to #18

this adds a type stub that indicates the methods added by the base cython graph class. I have some thoughts on how to improve this in the future (perhaps turning Graph itself into a factory function rather than a base class...) but will do that later

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.19178% with 13 lines in your changes missing coverage. Please review.

Project coverage is 91.10%. Comparing base (1a465ed) to head (24d6f8c).

Files with missing lines	Patch %	Lines
src/spatial_graph/graph/graph.py	80.76%	10 Missing ⚠️
src/spatial_graph/spatial_graph.py	85.71%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #31      +/-   ##
==========================================
- Coverage   94.63%   91.10%   -3.53%     
==========================================
  Files           9        9              
  Lines         298      326      +28     
==========================================
+ Hits          282      297      +15     
- Misses         16       29      +13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[codspeed-hq]

CodSpeed Performance Report

Merging #31 will not alter performance

_{Comparing tlambert03:typing2 (24d6f8c) with main (1a465ed)}

Summary

✅ 6 untouched benchmarks

[tlambert03]

all count_ methods should go to num_ methods