Add Github Actions workflow for RSpec

.github/workflows/rspec.yml

@@ -0,0 +1,28 @@
+name: RSpec
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        gemfile: [ rails-5.2, rails-6.0, rails-6.1 ]
+        ruby: [ '2.7' ]
+        include:
+          - gemfile: rails-6.1
+            ruby: '3.0'
+          - gemfile: rails-7.0
+            ruby: '2.7'
+          - gemfile: rails-7.0
+            ruby: '3.0'
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/${{ matrix.gemfile }}.gemfile
+    steps:
+    - uses: actions/checkout@v3
+    - uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
+    - run: bundle exec rake