Bump Node to v20 and add .nvmrc

[lucacome]

Proposed changes

Problem: We don't have a way to keep track of Node version and we're not using the latest LTS

Solution: Add .nvmrc, set it to v20 and use it in the Workflows and Makefile.
Also uploads code coverage for the modules.

Note: Switched to vitest because c8 was generating invalid coverage report, and didn't seem to read any configuration files.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

NONE

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.27%. Comparing base (2b0a255) to head (ea7752b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1627      +/-   ##
==========================================
+ Coverage   85.71%   86.27%   +0.55%     
==========================================
  Files          83       84       +1     
  Lines        5181     5390     +209     
  Branches        0       52      +52     
==========================================
+ Hits         4441     4650     +209     
  Misses        689      689              
  Partials       51       51              

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