Update ruby.yml

.github/workflows/ruby.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['3.1']
+        ruby-version: ['3.0', '3.1', '2.7']
 
     steps:
     - uses: actions/checkout@v3
@@ -35,4 +35,6 @@ jobs:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically
     - name: Run tests
-      run: bundle exec rake
+      run: bundle install
+    - name: Rubocop
+      run: rubocop