Replace CircleCI config with GH Actions CI workflow

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+name: ci
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        ruby-version:
+          - '2.7'
+          - '3.0'
+          - '3.1'
+
+    name: test (ruby ${{ matrix.ruby-version }})
+
+    permissions:
+      contents: read
+      checks: write
+
+    env:
+      LATEST_RUBY_VERSION: '3.1'
+      BUNDLE_DEPLOYMENT: true
+      BUNDLE_CACHE_ALL: true
+      BUNDLE_ONLY: default test
+      CI: true
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+          bundler-cache: true
+
+      - run: bundle lock
+
+      - run: bundle cache --no-install
+        env:
+          BUNDLE_DEPLOYMENT: false
+
+      - run: bundle check || bundle install --local
+
+      - run: bundle exec rake test