feat: Unsupported versions in the API and downloads

[naveensrinivasan]

• Implemented a feature unsupported packages are not downloaded
• Unsupported packages are part of the JSON API.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 90.00000% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.99%. Comparing base (a8b0625) to head (86e2aeb).

Files with missing lines	Patch %	Lines
internal/sitegen/simple.go	89.23%	2 Missing and 5 partials ⚠️
internal/config/unsupported.go	94.11%	1 Missing and 1 partial ⚠️
internal/sitegen/generator.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #60      +/-   ##
==========================================
+ Coverage   47.30%   47.99%   +0.69%     
==========================================
  Files          50       51       +1     
  Lines        7420     7505      +85     
==========================================
+ Hits         3510     3602      +92     
+ Misses       3508     3500       -8     
- Partials      402      403       +1     

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