Add newer rubies to CI matrix

Author: mjankowski

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["2.7", "3.0", "3.1", "3.2", "3.3"]
+        ruby: ["2.7", "3.0", "3.1", "3.2", "3.3", "3.4", "4.0"]
     steps:
       - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1