feat: add TypeScript types

[G-Rath]

Checks

• I have read the contributing guidelines.

Changes

• adds types so that usage with eslint.config.js in TypeScript codebases don't result in errors

Context

Now that plugins are imported "naturally" they can be type-checked by TypeScript so it's useful to ship types - for now I've just manually typed the plugin since primarily the only useful thing to have typed is the configs, as things like rules and settings are still not implicitly inferred and trying to automate this would be overkill.

These types match those that we've got in eslint-plugin-jest, eslint-plugin-jest-dom, and other places

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.33%. Comparing base (93a6ab9) to head (7cc514f).
Report is 27 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #963      +/-   ##
==========================================
+ Coverage   96.23%   96.33%   +0.09%     
==========================================
  Files          44       46       +2     
  Lines        2419     2481      +62     
  Branches     1000     1028      +28     
==========================================
+ Hits         2328     2390      +62     
  Misses         91       91              

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[Belco90]

Thanks! I'll autogenerate this with tsup when I finish my pending task for setting up a proper bundle to export CJS and ESM formats.

[github-actions]

🎉 This PR is included in version 6.5.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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