Enable permissive `max-len` and `max-lines` as warning

- Closes https://github.com/xojs/xo/issues/738 I think it might make sense to enable them as warning to look at the pushback without creating too much trouble. I think 200ch is a good upper limit, but I'm not sure about "1000 lines", especially in files with inline documentation and licensing. https://eslint.org/docs/v8.x/rules/max-lines https://eslint.org/docs/v8.x/rules/max-len