ci: codecov adjusments

[50rayn]

• add .nvmrc file to ensure the correct node version
• add packageManager key in package.json
• adjust ci config to new codecov action

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.62%. Comparing base (5fd5956) to head (4c1f459).
Report is 3 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   96.25%   96.62%   +0.37%     
==========================================
  Files           1        1              
  Lines          80       89       +9     
  Branches       17       20       +3     
==========================================
+ Hits           77       86       +9     
  Misses          2        2              
  Partials        1        1              

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