chore(linting): implement ESLint flat config compatibility for `eslint-plugin-turbo` (#9426)
### Description
- Add "flat/recommended" config to `eslint-plugin-turbo`
- Add `meta` property to plugin
- Update README.md accordingly with information on using flat config
- Add tests for flat config in `__tests__/cwdFlat.test.ts`
### Testing Instructions
Run the following command:
```shell
pnpm run test --filter=eslint-plugin-turbo
```
See vercel/turborepo#8606
Co-authored-by: Anthony Shew <anthony.shew@vercel.com>