Adds GitHub action to run tests

.github/workflows/test.yml

@@ -0,0 +1,28 @@
+name: Test
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - uses: actions/cache@preview
+      id: cache
+      with:
+        path: ~/local/rubies
+        key: ruby-2.6.5
+    - uses: clupprich/ruby-build-action@master
+      id: ruby
+      with:
+        ruby-version: 2.6.5
+        cache-available: ${{ steps.cache.outputs.cache-hit == 'true' }}
+    - name: Print version
+      run: ${{ steps.ruby.outputs.ruby-path }} --version
+    - name: Build and test with Rake
+      run: |
+        gem install bundler
+        bundle install --jobs 4 --retry 3 --without production
+        bundle exec rails test