docs: add css naming convention

[Ayase-252]

Refs: #42

[codecov]

Codecov Report

Merging #43 (b93804b) into master (088bc2e) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #43      +/-   ##
==========================================
+ Coverage   98.52%   98.56%   +0.03%     
==========================================
  Files          10       10              
  Lines         272      279       +7     
  Branches       35       35              
==========================================
+ Hits          268      275       +7     
  Misses          4        4              

Impacted Files	Coverage Δ
packages/website/src/api/request.ts	91.66% <0.00%> (-0.34%)	⬇️
packages/website/src/App.tsx	100.00% <0.00%> (ø)
packages/design/components/Tab/index.tsx	100.00% <0.00%> (ø)
packages/design/components/Button/index.tsx	100.00% <0.00%> (ø)
packages/design/components/Divider/index.tsx	100.00% <0.00%> (ø)

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[github-actions]

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