feat: Enable export validation

[just-boris]

Issue #, if available:

Description of changes:

Activate this feature: https://github.com/cloudscape-design/components/blob/e6c589ba5c8e5fa58f05b5e000561979f895f4f3/build-tools/tasks/docs.js#L28-L31

There will be an error if any accidental export happens

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.55%. Comparing base (f19fb72) to head (e8001c3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #62      +/-   ##
==========================================
+ Coverage   90.52%   90.55%   +0.03%     
==========================================
  Files          16       16              
  Lines         517      519       +2     
  Branches      136      146      +10     
==========================================
+ Hits          468      470       +2     
+ Misses         49       47       -2     
- Partials        0        2       +2     

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