Add Ruby 3.3 tests

Update CI file to add Ruby 3.3 to the tests matrix

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [3.1, 3.2]
+        ruby: [3.1, 3.2, 3.3]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4