Optimize CI Jobs

[jslee02]

• Replace CI jobs for Ubuntu (apt), macOS (homebrew), and Windows (vcpkg) with equivalent testing via Pixi to simplify CI maintenance.
• Add a "Getting Started" section to README.md.

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Before creating a pull request

• Document new methods and classes
• Format new code files using ClangFormat by running make format
• Build with -DDART_TREAT_WARNINGS_AS_ERRORS=ON and resolve all the compile warnings

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
• Add Python bindings for new methods and classes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.55%. Comparing base (ad50867) to head (d044bf4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1875   +/-   ##
=======================================
  Coverage   61.55%   61.55%           
=======================================
  Files         490      490           
  Lines       46013    46013           
=======================================
+ Hits        28322    28325    +3     
+ Misses      17691    17688    -3     

see 1 file with indirect coverage changes