build: convert eslint.config to typescript and add our plugin

[michaelfaith]

PR Checklist

• Addresses an existing open issue: fixes 🛠 Tooling: Migrate eslint.config.js to typescript #1099
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

This change migrates the eslint config to typescript, and adds our plugin's recommended config.

Tested locally to verify our plugin is working as expected. (This'll be great as an e2e smoke test)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.68%. Comparing base (3da9d12) to head (b0ebeb1).
Report is 8 commits behind head on main.

Additional details and impacted files

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##             main    #1112   +/-   ##
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  Coverage   99.68%   99.68%           
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  Files          22       22           
  Lines        1564     1564           
  Branches      205      205           
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  Hits         1559     1559           
  Misses          5        5           

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[michaelfaith]

@JoshuaKGoldberg You mentioned some warnings that you weren't a fan of (a reason to maybe wait until the next node release). What warnings were you talking about? ESLint's typescript config support relies on jiti. Unless you meant doing it without installing jiti?

[michaelfaith]

This was necessary after adding our plugin to the root config. Without this, eslint was using our config in the root as part of this test (which wasn't really good to begin with)

[JoshuaKGoldberg]

I bet after a while we'll be able to drop this too.

• Change Request: Use native Node.js TypeScript loading for eslint.config.ts? eslint/eslint#19357
• module: remove experimental warning from type stripping nodejs/node#58643

[JoshuaKGoldberg]

warnings that you weren't a fan of ... Unless you meant doing it without installing jiti?

Exactly: the warnings aren't there when tools like ESLint use runners/transpilers such as jiti. I just meant running a .ts file natively in Node.js with the native type stripping:

echo "console.log(123)" > index.ts
node index.ts

(node:50354) ExperimentalWarning: Type Stripping is an experimental feature and might change at any time
(Use `node --trace-warnings ...` to show where the warning was created)

👍 that that's not an issue here since the PR has ESLint using jiti.

[JoshuaKGoldberg]

🙌 Great!

[github-actions]

🎉 This is included in version v0.40.0 🎉

The release is available on:

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

Cheers! 📦🚀