feat(rehype-shikiji): add custom cache option

[wststone]

Description

feat: add custom cache option in rehype-shikiji

Linked Issues

fix #79

Additional context

[netlify]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3c23f1e) 92.39% compared to head (0b56396) 92.42%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #80      +/-   ##
==========================================
+ Coverage   92.39%   92.42%   +0.03%     
==========================================
  Files          52       52              
  Lines        4534     4556      +22     
  Branches      531      535       +4     
==========================================
+ Hits         4189     4211      +22     
  Misses        340      340              
  Partials        5        5              

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