fix: typeof openKeys can be React.Key

[xyuanbuilds]

when get keys in onOpenChange to set openKeys, type mismatch. maybe use React.Key is better.

[codecov[bot]]

Codecov Report

Merging #347 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #347   +/-   ##
=======================================
  Coverage   95.49%   95.49%           
=======================================
  Files          11       11           
  Lines         888      888           
  Branches      265      265           
=======================================
  Hits          848      848           
  Misses         40       40           

Impacted Files	Coverage Δ
src/Menu.tsx	98.12% <ø> (ø)

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