Replaced Travis-CI with GHA.

.github/workflows/test.yml

@@ -0,0 +1,30 @@
+---
+name: test
+on: [push, pull_request]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        entry:
+          - { ruby: '2.3', allowed-failure: false }
+          - { ruby: '2.4', allowed-failure: false }
+          - { ruby: '2.5', allowed-failure: false }
+          - { ruby: '2.6', allowed-failure: false }
+          - { ruby: '2.7', allowed-failure: false }
+          - { ruby: '3.0', allowed-failure: false }
+          - { ruby: '3.1', allowed-failure: false }
+          - { ruby: '3.2', allowed-failure: false }
+          - { ruby: 'ruby-head', allowed-failure: true }
+          - { ruby: 'truffleruby-head', allowed-failure: true }
+          - { ruby: 'jruby-head', allowed-failure: true }
+    name: test (${{ matrix.entry.ruby }})
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.entry.ruby }}
+      - run: bundle install --jobs=3 --retry=3 --path=vendor/bundle
+      - run: bundle exec rake spec
+        continue-on-error: ${{ matrix.entry.allowed-failure }}