CI: Migrate to GitHub Actions (#11)

Fix #9

Thanks Travis CI for providing free CI resource so far!

---------

Co-authored-by: Sutou Kouhei <kou@cozmixng.org>

Author: Watson1978

.github/workflows/test.yml

@@ -0,0 +1,37 @@
+name: Test
+
+on:
+  push:
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  ruby-versions:
+    uses: ruby/actions/.github/workflows/ruby_versions.yml@master
+    with:
+      engine: cruby
+      min_version: 2.7
+
+  test:
+    needs: ruby-versions
+    name: ${{ matrix.os }} ${{ matrix.ruby }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
+        os:
+          - ubuntu-latest
+          - macos-latest
+    steps:
+      - uses: actions/checkout@v6
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+
+      - name: Run tests
+        run: bundle exec rake