Add Ruby 3.3 to CI.

Author: nashby

.github/workflows/ruby.yml

@@ -32,7 +32,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby-version: ['3.0', '3.1', '3.2']
+        ruby-version: ['3.0', '3.1', '3.2', '3.3']
         test: ['minitest', 'rspec']
         gemfile:
           - Gemfile.rails61