Update to a single package with ESLint 9 flat configs 🚀

[malparty]

Why

• The current mono-repo is heavy to maintain. Having a single npm package would make updates lighter.
• The current config is NOT compatible with ESLint 9
• Flat configs are more flexible as they are basic JS objects and can be composed, thus giving more freedom to client apps
• Many dependencies are outdated which expose the client apps to security vulnerabilities, ESLint 9 update is now a MUST.