Enable CI

.github/workflows/ci.yml

@@ -0,0 +1,30 @@
+name: Ruby CI
+
+on:
+  push:
+    branches:
+      - "main"
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        ruby-version: ["3.3", "3.2", "3.1", "3.0"]
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Ruby ${{ matrix.ruby-version }}
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+      - name: Install dependencies
+        run: bundle install
+      - name: Run tests
+        run: bundle exec rspec