feat(scrollbar): add some variables

[Talljack]

close #649

[vercel]

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[codecov]

Codecov Report

Merging #679 (e55057e) into main (a41a163) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #679      +/-   ##
==========================================
- Coverage   39.20%   39.19%   -0.01%     
==========================================
  Files         507      507              
  Lines       12345    12343       -2     
  Branches     3454     3454              
==========================================
- Hits         4840     4838       -2     
  Misses       6597     6597              
  Partials      908      908              

Impacted Files	Coverage Δ
src/_styles/common/dark.ts	100.00% <ø> (ø)
src/_styles/common/light.ts	100.00% <ø> (ø)
src/scrollbar/src/ScrollBar.tsx	36.19% <ø> (-0.48%)	⬇️

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