fix(types): stricter but internal types

[JounQin]

No description provided.

[changeset-bot]

🦋 Changeset detected

Latest commit: 3e1cce4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
synckit	Patch

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[codecov]

Codecov Report

Merging #32 (3e1cce4) into main (67af7c3) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #32   +/-   ##
=======================================
  Coverage   97.43%   97.43%           
=======================================
  Files           1        1           
  Lines          78       78           
  Branches       25       24    -1     
=======================================
  Hits           76       76           
  Misses          2        2           

Impacted Files	Coverage Δ
src/index.ts	97.43% <100.00%> (ø)

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