chore(lib): remove all os.path in favor to pathlib

[jeertmans]

No description provided.

[codecov]

Codecov Report

Patch coverage: 31.42% and project coverage change: +0.10 🎉

Comparison is base (a7719db) 58.26% compared to head (8efbfc2) 58.36%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #225      +/-   ##
==========================================
+ Coverage   58.26%   58.36%   +0.10%     
==========================================
  Files          14       14              
  Lines        1718     1715       -3     
==========================================
  Hits         1001     1001              
+ Misses        717      714       -3     

Impacted Files	Coverage Δ
manim_slides/config.py	74.15% <0.00%> (-0.15%)	⬇️
manim_slides/slide.py	49.45% <16.66%> (+0.80%)	⬆️
manim_slides/present.py	56.28% <50.00%> (ø)
manim_slides/defaults.py	100.00% <100.00%> (ø)

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