feat(core): drop border widths slice

[gabrieleAngius]

Proposed changes

dropping border width slice and remove all box-related logic due to upcoming changes related to variables

wip #25

Types of changes

• ✨ New feature (non-breaking change which adds functionality or enhancements)
• 🐛 Bugfix (non-breaking change which fixes an issue)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• ✅ Tests (added tests for an existing feature)
• 📚 Chore / Documentation Update (if none of the other choices apply)
• 🙌 Other (please, write a clear and concise description of the proposal in the section above)

Checklist

• ✂️ I have ensured that the PR is concise and broken down if needed
• 👀 I have read the README doc
• 🧪 I have added tests that prove my fix is effective or that my feature works
• 📚 I have added necessary documentation (if appropriate)
• 🔀 Any dependent changes have been merged and published in downstream modules

Further comments

See #25 for more context

[codecov]

Codecov Report

Patch coverage: 80.00% and project coverage change: -8.29 ⚠️

Comparison is base (dea53c6) 98.64% compared to head (87d0485) 90.36%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #26      +/-   ##
==========================================
- Coverage   98.64%   90.36%   -8.29%     
==========================================
  Files          24       13      -11     
  Lines         444      218     -226     
  Branches       83       41      -42     
==========================================
- Hits          438      197     -241     
- Misses          6       20      +14     
- Partials        0        1       +1     

Impacted Files	Coverage Δ
widget-src/constants.ts	100.00% <ø> (ø)
widget-src/types.ts	100.00% <ø> (ø)
widget-src/utils/downloadTheme.ts	100.00% <ø> (ø)
widget-src/hooks/useInitTheme.ts	22.22% <66.66%> (-75.61%)	⬇️
widget-src/parsers/sliceItemsToMorfeo.ts	100.00% <100.00%> (ø)

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