Support Eslint 9

[tcastelly]

Since Eslint 9, flat config has to be used: https://eslint.org/docs/latest/use/configure/configuration-files

Right now we have errors like this:

ESLint: 9.0.0

A config object is using the "extends" key, which is not supported in flat config system.

Instead of "extends", you can include config objects that you'd like to extend from directly in the flat config array.

Please see the following page for more information:
https://eslint.org/docs/latest/use/configure/migration-guide#predefined-and-shareable-configs

[PurpleTape]

Any updates? 🥺🥺🥺