feat: type module, native fetch, vitest

[bschlenk]

Now fully type: module. Replaced fetch-ponyfill with native fetch. Tests rewritten to use vitest. Eslint config updated to
@bschlenk/eslint-config. All dependencies upgraded to the latest. Switched to pnpm.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (825d854) to head (e360a53).

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Additional details and impacted files

@@            Coverage Diff             @@
##            master      #270    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files            6         9     +3     
  Lines          236       392   +156     
  Branches        30       105    +75     
==========================================
+ Hits           236       392   +156     

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