ci: add Ruby 3.3.0 to the test matrix (#50)

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [2.5, 2.6, 2.7, '3.0', 3.1, 3.2, head]
+        ruby: [2.5, 2.6, 2.7, '3.0', 3.1, 3.2, 3.3, head]
     steps:
       - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1