Add GH workflow for tests

.github/workflows/test.yml

@@ -0,0 +1,20 @@
+name: Automated tests
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  test:
+    name: test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.1'
+          bundler-cache: true
+      - run: bundle exec rspec