Load rake tasks from voxpupuli-rubocop

We do the same on all our other gems.

Rakefile

@@ -57,16 +57,10 @@ end
 
 task update: %i[update_common_tests update_meta_schemas]
 
-require 'rubocop/rake_task'
-RuboCop::RakeTask.new(:rubocop) do |task|
-  # These make the rubocop experience maybe slightly less terrible
-  task.options = ['-D', '-S', '-E']
-
-  # Use Rubocop's Github Actions formatter if possible
-  if ENV['GITHUB_ACTIONS'] == 'true'
-    rubocop_spec = Gem::Specification.find_by_name('rubocop')
-    task.formatters << 'github' if Gem::Version.new(rubocop_spec.version) >= Gem::Version.new('1.2')
-  end
+begin
+  require 'voxpupuli/rubocop/rake'
+rescue LoadError
+  # the voxpupuli-rubocop gem is optional
 end
 
 task default: :test