Try against Ruby main

Author: andyw8

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
         gemfile:
           - Gemfile
           - gemfiles/Gemfile-rails-main
-        ruby: ["3.0", "3.1", "3.2", "3.3", "head"]
+        ruby: ["3.0", "3.1", "3.2", "3.3", "head", "main"]
         include:
           - ruby: "head"
             experimental: true