Add Rubocop to CI

.github/workflows/CI.yml

@@ -3,6 +3,27 @@ name: Ruby
 on: [push, pull_request]
 
 jobs:
+  lint:
+    name: CI-lint
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby:
+          - '3.1'
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+
+      - name: Lint
+        run: |
+          bundle exec rubocop
+
   test:
     name: CI-tests
     runs-on: ubuntu-latest