Add rubocop spacing rules

We were following these rules in most places; we just didn't define them
anywhere.

spec/factories/administration.rb

@@ -17,7 +17,7 @@ FactoryBot.define do
   factory :banner do
     sequence(:title) { |n| "Banner title #{n}" }
     sequence(:description) { |n| "This is the text of Banner #{n}" }
-    target_url {["/proposals", "/debates" ].sample}
+    target_url { ["/proposals", "/debates"].sample }
     post_started_at { Time.current - 7.days }
     post_ended_at { Time.current + 7.days }
     background_color { "#FF0000" }