Fix prediction bug, lazyloading bug; update plotting function; update docs.

[chenyangkang]

The main bugs fixed:

1. [BUG] IndexError: single positional indexer is out-of-bounds #82
2. A previous bug: after getting an attribute of a LazyLoadingEstimator object, the model was not auto-dumped. This is now fixed.

[codecov]

Codecov Report

❌ Patch coverage is 82.01439% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.57%. Comparing base (664a13f) to head (f5da089).
⚠️ Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
stemflow/utils/plot_gif.py	75.71%	17 Missing ⚠️
stemflow/model/AdaSTEM.py	87.27%	7 Missing ⚠️
stemflow/lazyloading/lazyloading.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
- Coverage   90.97%   90.57%   -0.40%     
==========================================
  Files          40       40              
  Lines        3566     3587      +21     
==========================================
+ Hits         3244     3249       +5     
- Misses        322      338      +16     

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