Support ESLint new's flat config

[felipecrs]

Clear and concise description of the problem

ESLint is migrating from eslintrc to eslint.config.js, with ESM support.

Suggested solution

It would be nice if the eslint configs from this repository could add support for it too.

Alternative

No response

Additional context

No response

Validations

• Follow the Code of Conduct.
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.