added nhood_clustering

[julienmortier]

This PR contains 2 functions to do neighborhood clustering (using K-means clustering) based on the cell type composition of neighboring cells. It is similar to what is possible in Scimap (https://scimap.xyz/tutorials/md/spatial_lda_scimap/) and ark-analysis. The current implementation is still somewhat slow so improvements are definitely still possible. A similar approach using LDA would also be interesting in the future.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.26%. Comparing base (3ce0b49) to head (ac8686d).

Files with missing lines	Patch %	Lines
src/harpy/table/_nhood_clustering.py	0.00%	35 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #160      +/-   ##
==========================================
- Coverage   61.58%   61.26%   -0.33%     
==========================================
  Files          91       92       +1     
  Lines        6677     6712      +35     
  Branches     1060     1061       +1     
==========================================
  Hits         4112     4112              
- Misses       2131     2166      +35     
  Partials      434      434              

Files with missing lines	Coverage Δ
src/harpy/table/_nhood_clustering.py	0.00% <0.00%> (ø)

🚀 New features to boost your workflow:

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