enable GH Actions

.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+name: CI
+
+on: [push]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    name: ubuntu-ruby-${{ matrix.ruby-version }}
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby-version: ["3.3", "3.2", "3.1", "3.0", "2.7", "2.6", "2.5"]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+          bundler-cache: true
+      - name: Runs tests
+        run: bundle exec rake test