chore: don't fix with lint target

[nschonni]

Since the lint target is called with the --fix parameter, the CI wouldn't fail if there were autofixable issues. Split the fix vs lint targets, and reused Prettiers ignore file instead of creating a .eslintignore file

[eemeli]

Rather than changing the behaviour of npm run lint, it'd be better to change the command used in CI to directly call npx eslint without the --fix argument.