add CI

.github/workflows/ruby.yml

@@ -0,0 +1,35 @@
+--
+name: CI
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: ['3.1', '3.2', '3.3']
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true
+
+    - name: Lint
+      run: bundle exec rake rubocop
+
+    - name: Build
+      run: bundle exec rake
+
+    - name: Test
+      run: bundle exec rake test