Add niche identification tutorial

[Marius1311]

Updates the existing tutorial using recent changes, and adds a new tutorial on niche identification.

[codecov]

Codecov Report

❌ Patch coverage is 28.57143% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.05%. Comparing base (8a708f6) to head (a8303fc).
⚠️ Report is 177 commits behind head on main.

Files with missing lines	Patch %	Lines
src/cellmapper/evaluate.py	28.57%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
- Coverage   85.22%   84.05%   -1.17%     
==========================================
  Files           7        7              
  Lines         609      621      +12     
==========================================
+ Hits          519      522       +3     
- Misses         90       99       +9     

Files with missing lines	Coverage Δ
src/cellmapper/evaluate.py	80.00% <28.57%> (-4.46%)	⬇️

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