Improve CI GitHub Action

- Update checkout action to v3. Node.js 12 actions are deprecated
- Test against Ruby 3.2
- Test against Ruby and Rails head to detect breaking changes and deprecation
  in advantage. Mark runs as experimental, so they are allowed to fail

.github/workflows/ci.yml

@@ -6,24 +6,43 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        ruby: ['2.7', '3.0', '3.1', '3.2']
+        gemfile: [ rails_7_0 ]
+        channel: ['stable']
+
         include:
           - gemfile: rails_7_0
-            ruby: 2.7
-          - gemfile: rails_7_0
-            ruby: 3.0
-          - gemfile: rails_7_0
-            ruby: 3.1
+            ruby: head
+            channel: 'experimental'
+          - gemfile: rails_edge
+            ruby: '2.7'
+            channel: 'experimental'
+          - gemfile: rails_edge
+            ruby: '3.0'
+            channel: 'experimental'
+          - gemfile: rails_edge
+            ruby: '3.1'
+            channel: 'experimental'
+          - gemfile: rails_edge
+            ruby: '3.2'
+            channel: 'experimental'
+          - gemfile: rails_edge
+            ruby: head
+            channel: 'experimental'
+
+    continue-on-error: ${{ matrix.channel != 'stable' }}
 
     name: ${{ matrix.gemfile }}, ruby ${{ matrix.ruby }}
     env:
       BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/${{ matrix.gemfile }}.gemfile
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
+        rubygems: latest
         bundler-cache: true
 
     - name: Run specs