Add RuboCop extensions?

[dentarg]

Since some versions back, RuboCop suggests some extensions we could use:

Tip: Based on detected gems, the following RuboCop extension libraries might be helpful:
  * rubocop-minitest (http://github.com/rubocop/rubocop-minitest)
  * rubocop-rake (http://github.com/rubocop/rubocop-rake)
  * rubocop-sequel (http://github.com/rubocop/rubocop-sequel)

You can opt out of this message by adding the following to your config (see https://docs.rubocop.org/rubocop/extensions.html#extension-suggestions for more options):
  AllCops:
    SuggestExtensions: false