Add a GitHub Actions CI

.github/dependabot.yml

@@ -0,0 +1,7 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      # Check for updates to GitHub Actions every weekday
+      interval: "daily"

.github/workflows/ci.yml

@@ -0,0 +1,36 @@
+me: Ruby CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  test:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        ruby-version:
+          - 3.2
+          - 3.1
+          - "3.0"
+        gemfile:
+          - gemfiles/rspec_3.3.gemfile
+          - gemfiles/rspec_3.4.gemfile
+          - gemfiles/rspec_3.5.gemfile
+          - gemfiles/rspec_3.6.gemfile
+          - gemfiles/rspec_3.7.gemfile
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Ruby ${{ matrix.ruby-version }}
+        uses: ruby/setup-ruby@v1
+        gemfile: ${{ matrix.gemfile }}
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+          bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+      - name: Run tests
+        run: bundle exec rake