Update documentation Makefile and README

[ADubhlaoich]

Proposed changes

This commit updates the documentation Makefile and README, removing references to Netlify and clarifying the usage of the Makefile. This is part of an effort to ensure they remain consistent across all NGINX repositories.

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.21%. Comparing base (454e5c1) to head (3dcd6ef).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2507   +/-   ##
=======================================
  Coverage   89.21%   89.21%           
=======================================
  Files         100      100           
  Lines        7539     7539           
  Branches       50       50           
=======================================
  Hits         6726     6726           
  Misses        756      756           
  Partials       57       57           

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[ADubhlaoich]

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