Fix type support for readonly arrays

[JounQin]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything or linked relevant results below
• I made sure the docs are up to date
• I included tests (or that’s not needed)

Description of changes

close #39

[Copilot]

Pull Request Overview

Fixes TypeScript type support for readonly arrays by updating the type definition to handle ReadonlyArray<any> instead of just Array<any> and improves array element type access.

• Updated the Matches type definition to support readonly arrays
• Changed array element access from Check[keyof Check] to Check[number] for better type inference
• Added comprehensive test coverage for both mutable and readonly array scenarios

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
lib/index.js	Updated TypeScript type definition to support readonly arrays and improved array element access
index.test-d.ts	Added test cases to verify type behavior with both mutable and readonly arrays

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[glebec]

@remcohaszing et al – any blockers to getting this merged?

[glebec]

Thanks for the merge @wooorm — can we also get a release? 🙏

[wooorm]

right, 5.1.0!