Use this config in all DaWanda Ruby projects

[fanaugen]

Currently we reference it in most of them with the notable exception of ❤️OS-frontend.

In frontend’s Rubocop config there are some rules that are the exact opposite of what we enforce in this repo (and therefore in ❤️OS-backend). For instance, %w(foo bar) in frontend vs. Batsov’s default elsewhere. This is confusing and conterproductive for anyone who works on both projects.

I think we should resolve #3 first:

• Agree on Rubocop rules that we should disable
• Use this config in frontend