ci: test against ruby 3.4

Fixes #21

Author: gi

.github/workflows/ci.yml

@@ -63,10 +63,11 @@ jobs:
           - macos-latest
           - ubuntu-latest
         ruby:
-          - ruby-2.6
-          - ruby-2.7
           - ruby-3.0
           - ruby-3.1
+          - ruby-3.2
+          - ruby-3.3
+          - ruby-3.4
           # - jruby
           # - truffleruby
     runs-on: ${{ matrix.os }}