Use Github Actions for tests

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: CI
+on:
+  push:
+    branches: [ $default-branch ]
+  pull_request:
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby: ['2.5', '2.6', '2.7']
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up Ruby ${{ matrix.ruby }}
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - name: Set up Node
+        uses: actions/setup-node@v2-beta
+        with:
+          node-version: '14'
+      - name: Install dependencies
+        run: bundle install --without production
+      - name: Run tests
+        run: bundle exec rake
+        env:
+          RAILS_ENV: test