Add RuboCop

.github/workflows/rubocop.yml

@@ -0,0 +1,17 @@
+name: RuboCop
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout source code
+        uses: actions/checkout@v2
+      - name: Setup ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      - name: Run RuboCop
+        run: bundle exec rubocop --format github --parallel