Merge pull request #798 from y-yagi/ci-against-ruby33

CI against Ruby 3.3

Author: jnunemaker

.github/workflows/ci.yml

@@ -14,6 +14,7 @@ jobs:
           - '3.0' # Quoted, to avoid YAML float 3.0 interplated to "3"
           - 3.1
           - 3.2
+          - 3.3
     steps:
       - name: Check out repository code
         uses: actions/checkout@v3