Add CI

.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+name: CI
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby: ['3.2', '3.1', '3.0', '2.7', '2.6', '2.5']
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+
+      - run: bundle exec rake