Fix Issue #21044

[bupd]

Thank you for contributing to Harbor!

Comprehensive Summary of your change

This issue is not present in the LTS version of nodejs updating doc to use the correct node version.

• added .nvmrc
• updated docs to be clear for newcomers.

Issue being fixed

Fixes #21044

Please indicate you've done the following:

• Well Written Title and Summary of the PR
• Label the PR as needed. "release-note/ignore-for-release, release-note/new-feature, release-note/update, release-note/enhancement, release-note/community, release-note/breaking-change, release-note/docs, release-note/infra, release-note/deprecation"
• Accepted the DCO. Commits without the DCO will delay acceptance.
• Made sure tests are passing and test coverage is added if needed.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed in website repository.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.08%. Comparing base (c8c11b4) to head (b9f97eb).
Report is 327 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #21153       +/-   ##
===========================================
+ Coverage   45.36%   66.08%   +20.71%     
===========================================
  Files         244     1049      +805     
  Lines       13333   114649   +101316     
  Branches     2719     2867      +148     
===========================================
+ Hits         6049    75766    +69717     
- Misses       6983    34739    +27756     
- Partials      301     4144     +3843     

Flag	Coverage Δ
unittests	66.08% <ø> (+20.71%)	⬆️

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see 1288 files with indirect coverage changes

[MinerYang]

Please refer to #21044 (comment)

[bupd]

@MinerYang update .nvmrc to the supported version.