Add rubocop config

previously this gem only contained a rubocop config that's used in our
modules. We didn't run rubocop for the ruby code in this exact gem. This
is changed with this commit.

.github/workflows/test.yml

@@ -10,6 +10,17 @@ env:
   BUNDLE_WITHOUT: release
 
 jobs:
+  rubocop:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Ruby ${{ matrix.ruby }}
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: "3.3"
+          bundler-cache: true
+      - name: Run Rubocop
+        run: bundle exec rake rubocop
   test:
     runs-on: ubuntu-latest
     strategy:
@@ -45,6 +56,7 @@ jobs:
         run: bundle exec rake spec
   tests:
     needs:
+      - rubocop
       - test
     runs-on: ubuntu-latest
     name: Test suite

.rubocop.yaml

@@ -0,0 +1,3 @@
+---
+inherit_from:
+  - rubocop.yml

Rakefile

@@ -16,3 +16,13 @@ begin
   end
 rescue LoadError
 end
+
+# this is identical to our config in voxpupuli-rubocop, but that gem targets Ruby 2.7
+# and voxupuli-test depends on an older rubocop version because we provide it for our modules
+require 'rubocop/rake_task'
+RuboCop::RakeTask.new(:rubocop) do |task|
+  # These make the rubocop experience maybe slightly less terrible
+  task.options = ['--display-cop-names', '--display-style-guide', '--extra-details']
+  # Use Rubocop's Github Actions formatter if possible
+  task.formatters << 'github' if ENV['GITHUB_ACTIONS'] == 'true'
+end