dartpy: Add shadow technique

[jslee02]

Changes

• Add shadow technique
• Add OSG biped example
• Reduced default shadow map resolution

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Before creating a pull request

• Document new methods and classes
• Format new code files using clang-format

Before merging a pull request

• Set version target by selecting a milestone on the right side
• Summarize this change in CHANGELOG.md
• Add unit test(s) for this change

[codecov]

Codecov Report

Merging #1348 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1348      +/-   ##
==========================================
+ Coverage   56.88%   56.89%   +0.01%     
==========================================
  Files         366      366              
  Lines       27174    27174              
==========================================
+ Hits        15458    15461       +3     
+ Misses      11716    11713       -3

Impacted Files	Coverage Δ
dart/dynamics/Skeleton.cpp	66.12% <0%> (+0.16%)	⬆️