Two renovate configs in the same repo

[alexandr-g]

Describe the bug
I've noticed that we have two separate renovate configs at the root of the repository and they are extended from different sources. I suggest to merge them to avoid confusion.

1. https://github.com/signavio/kraken/blob/master/renovate.config.js

extends: [':library']

2. https://github.com/signavio/kraken/blob/master/renovate.json

"extends": ["config:base"]