docs(powered-by): add JSDoc

[yusukebe]

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.29%. Comparing base (89a0ac1) to head (6cb3818).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3520    +/-   ##
========================================
  Coverage   94.29%   94.29%            
========================================
  Files         157      157            
  Lines        9488     9488            
  Branches     2747     2877   +130     
========================================
  Hits         8947     8947            
  Misses        541      541            

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