move to GitHub actions

.github/workflows/ci.yml

@@ -0,0 +1,25 @@
+name: Test
+
+on:
+  push:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        ruby-version:
+          - 2.6
+          - 2.7
+          - 3.0
+          - 3.1
+          - 3.2
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+          bundler-cache: true
+
+      - run: bundle exec rake