[reading order] de-skew rotated layout geoms

[felixdittrich92]

This PR:

• Add de-skew method to ReadingOrderPredictor to handle also the rotation path
• Add cor tests and missing docu

[codecov]

Codecov Report

❌ Patch coverage is 97.14286% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.61%. Comparing base (ea46d99) to head (ce201cf).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
doctr/models/reading_order/base.py	97.14%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2115   +/-   ##
=======================================
  Coverage   96.61%   96.61%           
=======================================
  Files         168      168           
  Lines        9059     9094   +35     
=======================================
+ Hits         8752     8786   +34     
- Misses        307      308    +1     

Flag	Coverage Δ
unittests	96.61% <97.14%> (+<0.01%)	⬆️

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