Added Ruby 4.0 to the CI matrix.

Author: postmodern

.github/workflows/ruby.yml

@@ -14,6 +14,7 @@ jobs:
           - '3.2'
           - '3.3'
           - '3.4'
+          - '4.0'
           - jruby
           - truffleruby
     name: OS ${{ matrix.os }} / Ruby ${{ matrix.ruby }}