feat(eslint): add flat configs

[appano1]

Resolves #73
Resolves #108

Related to #113

The goal of this PR is to ensure that developers meet no breaking changes.
Developers can apply the flat config as follows.

import vercel from '@vercel/style-guide/eslint/flat'
export default [
  ...vercel.configs.recommended,
  ...vercel.configs.typescript,
  ...vercel.configs.react,
  ...vercel.configs.next,
]

Due to certain characteristics of the flat config, it is not fully identical to the legacy config. @vercel/style-guide/eslint/browser and @vercel/style-guide/eslint/node might not be needed since developers can register them through the globals package. Instead, developers can continue to use the existing _base.js by applying configs.recommended.

import vercel from '@vercel/style-guide/eslint/flat'
export default [
  ...vercel.configs.recommended,
  {
    languageOptions: {
      globals: {
        ...globals.browser,
        ...globals.node,
      },
    },
  },
]

For @vercel/style-guide/eslint/jest, I’ve added jest-typescript.js to increase flexibility, as users may need to configure it within the flat config using options.files.

import vercel from '@vercel/style-guide/eslint/flat'
export default [
  { files: [/*path*/], ...vercel.configs.jest },
  vercel.configs['jest-typescript'],
]

[socket-security]

New and removed dependencies detected. Learn more about Socket for GitHub ↗︎

Package	New capabilities	Transitives	Size	Publisher
npm/@eslint/js@9.14.0	None	0	14.6 kB	eslintbot
npm/@types/node@22.9.0	None	+1	2.36 MB	types
npm/@typescript-eslint/eslint-plugin@8.13.0	Transitive: environment, filesystem	+37	8.54 MB	bradzacher, jameshenry
npm/@typescript-eslint/parser@8.13.0	Transitive: environment, filesystem	+30	3.73 MB	bradzacher, jameshenry
npm/eslint-plugin-import@2.31.0	environment, filesystem, unsafe Transitive: eval	+102	8.45 MB	ljharb
npm/eslint-plugin-jest@28.9.0	filesystem Transitive: environment	+32	4.73 MB	simenb
npm/eslint-plugin-jsx-a11y@6.10.2	Transitive: eval	+91	12 MB	evcohen, jessebeach, lencioni, ...1 more
npm/eslint-plugin-playwright@2.0.0	None	+2	307 kB	mxschmitt
npm/eslint-plugin-react-hooks@5.0.0	None	0	0 B
npm/eslint-plugin-react@7.37.2	Transitive: environment, eval, filesystem	+113	8.48 MB	ljharb, yannickcr
npm/eslint-plugin-testing-library@6.4.0	Transitive: environment, filesystem	+44	3.97 MB	testing-library-bot
npm/eslint-plugin-tsdoc@0.3.0	Transitive: environment, eval, filesystem, unsafe	+15	4.74 MB	odspnpm
npm/eslint-plugin-unicorn@56.0.0	Transitive: environment, filesystem, shell, unsafe	+67	6.82 MB	sindresorhus
npm/eslint@9.14.0	environment Transitive: eval, filesystem, shell, unsafe	+84	10.4 MB	eslintbot
npm/globals@15.12.0	None	0	176 kB	sindresorhus
npm/prettier@3.3.3	environment, filesystem, unsafe	0	7.7 MB	prettier-bot

🚮 Removed packages: npm/@typescript-eslint/eslint-plugin@7.1.1, npm/@typescript-eslint/parser@7.1.1, npm/eslint-plugin-eslint-comments@3.2.0, npm/eslint-plugin-import@2.29.1, npm/eslint-plugin-jest@27.9.0, npm/eslint-plugin-jsx-a11y@6.8.0, npm/eslint-plugin-playwright@1.5.2, npm/eslint-plugin-react-hooks@4.6.0, npm/eslint-plugin-react@7.34.0, npm/eslint-plugin-testing-library@6.2.0, npm/eslint-plugin-tsdoc@0.2.17, npm/eslint-plugin-unicorn@51.0.1, npm/eslint-plugin-vitest@0.3.22, npm/eslint@8.57.0, npm/prettier@3.2.5

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[appano1]

I added a comments config and a unicorn config to ensure that only pure rules, excluding plugins, are in the rules directory.

[appano1]

I replaced eslint-comment to @eslint-community/eslint-comments cause eslint-comment is not maintained for a while