feat: support flat config#609

# !! IMPORTANT !! If user previously imported this package using ESM, `import { configs, rules } from 'eslint-plugin-compat'` will not work. This is a BREAKING CHANGE, so need to increase a major version to release it. If you agree to a major version upgrade, it would be good to also remove `config`. If you don't want to make a BREAKING CHANGE, I can maintain compatibility by splitting the package entry point into `.mts` and `.cts`. (I had implemented it once, but the code was too complicated, so I deleted it for now: https://github.com/amilajack/eslint-plugin-compat/commit/686d75a45bc84c33071ca36b5efb497fd0143044) Please feel free to let me know which method you prefer. :) ## What's Changed - Support flat config (Thank you for being a reference, [eslint-plugin-n](https://github.com/eslint-community/eslint-plugin-n)!) - Bump dependencies - Fix test errors with update snapshots - Replace [babel-eslint](https://github.com/babel/babel-eslint) to [@babel/eslint-parser](https://github.com/babel/babel/tree/main/eslint/babel-eslint-parser) (See: https://github.com/babel/babel-eslint#note-babel-eslint-is-now-babeleslint-parser-and-has-moved-into-the-babel-monorepo) - Deprecate named export - Provide type declaration Resolves: #603 P.S. [ESLint v9 has been released](https://github.com/eslint/eslint/releases/tag/v9.0.0). IMO, it's a good time to drop support for versions below ESLint v8.57.0!