Lint app via actions

.github/workflows/ruby.yml

@@ -3,6 +3,20 @@ name: Ruby
 on: [push]
 
 jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: Set up Ruby 2.6
+      uses: actions/setup-ruby@v1
+      with:
+        ruby-version: 2.6.x
+    - name: Build and test with Rake
+      run: |
+        gem install bundler -v 1.16
+        bundle install --jobs 4 --retry 3
+        bundle exec rubocop
+
   test:
     runs-on: ubuntu-latest
     strategy: