Remove @feltjs/eslint-config to fix build

[Dr-Electron]

Description of change

Sems like @feltjs/eslint-config doesn't exist anymore. Not sure if it was even used in this Project, I would have expected that you have to import it in some config. So if we never used it, we can just merge this.
If we used it, there seems to be a new version by the same maintainer here, but it only works with svelte >=4 and some other changes. But maybe we could just copy the config if we really need it. I will leave that up to you.

Type of change

• Bug fix (a non-breaking change which fixes an issue)

How the change has been tested

Run locally. Output seems to be the same.

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas

[Dr-Electron]

I just realised that this is probably how you import the feltjs config?
Should I just replace it by copying the "new" config from ryanatkn (I suppose it is the same or similar)?