Test against recent Ruby versions.

Author: ppostma

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: [2.3, 2.4, 2.5, 2.6, 2.7]
+        ruby-version: ['3.2', '3.3', '3.4', '4.0']
     steps:
     - uses: actions/checkout@v2
     - uses: ruby/setup-ruby@v1