Test with all supported Rails versions in CI

Author: mvz

.github/workflows/ruby.yml

@@ -26,6 +26,18 @@ jobs:
     strategy:
       matrix:
         ruby: ["3.2", "3.3", "3.4"]
+        gemfile:
+          - rails_61
+          - rails_70
+          - rails_71
+        exclude:
+          - ruby: "3.4"
+            gemfile: rails_61
+          - ruby: "3.4"
+            gemfile: rails_70
+
+    env:
+      BUNDLE_GEMFILE: gemfiles/${{ matrix.gemfile }}.gemfile
 
     steps:
       - uses: actions/checkout@v4