rm eslint

eslint 9 has recently been released. It has several breaking changes, especially with regards to configurations: https://eslint.org/docs/latest/use/migrate-to-9.0.0

We have a tiny amount of js code when compared to python. eslint is complex and slow and doesn't even find a lot of relevant issues. So I don't think it is worth keeping it around.

Unfortunately I have not been able to find a decent replacement. But given the tiny amount of JavaScript that we have, I think that is fine.