CI: Test against Ruby 3.4

Author: ledermann

.github/workflows/main.yml

@@ -17,10 +17,16 @@ jobs:
           - '3.1'
           - '3.2'
           - '3.3'
+          - '3.4'
         gemfile:
           - gemfiles/rails_6_1.gemfile
           - gemfiles/rails_7_0.gemfile
           - gemfiles/rails_7_1.gemfile
+        exclude:
+          - ruby_version: '3.4'
+            gemfile: gemfiles/rails_6_1.gemfile
+          - ruby_version: '3.4'
+            gemfile: gemfiles/rails_7_0.gemfile
 
     name: Ruby ${{ matrix.ruby_version }} / Gemfile ${{ matrix.gemfile }}