Migrate to `eslint.config.js`

[jasongitmail]

Describe the problem

SvelteKit currently uses .eslintrc.cjs, the outgoing format.

Describe the proposed solution

Switch to eslint.config.js and remove .eslintignore and .eslintrc.cjs.

Starting in v9, ESLint will use one config file named eslint.config.js, and it's possible to remove .eslintignore and specify ignored file patterns within the config.

Good info: https://eslint.org/blog/2022/08/new-config-system-part-2/

Comes with a bunch of benefits--including reducing config pollution within a project--and its easier to extend with custom user configs.

Alternatives considered

Will be required in v9 ESLint.

Importance

nice to have

Additional Information

Adding the issue to track it, so I can update existing projects similarly.

[teemingc]

I think we'll need to wait for the typescript-eslint parser to support flat configs before we can go ahead with this. More info here https://github.com/typescript-eslint/typescript-eslint/issues/7694#issuecomment-1854655034

[victormihalache]

Will such change be something the migration script will do anything about? At least emit a notice of sorts?

[polyzen]

No longer blocked https://typescript-eslint.io/blog/announcing-typescript-eslint-v7/

[lts20050703]

Any updates on this? Eslint v9 just got released a few hours ago

https://eslint.org/blog/2024/04/eslint-v9.0.0-released/

[WarningImHack3r]

I just tried migrating by myself EmeraldHQ/Website@29f3a15 (#227) But it seems that eslint-plugin-svelte isn't ready yet or that something is wrong in my attempt: I get lint errors (related to TypeScript I guess?), not sure why