Replace AppVeyor CI with GitHub Actions Windows runner

Author: hsbt

.github/workflows/ruby.yml

@@ -21,6 +21,7 @@ jobs:
     strategy:
       matrix:
         ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
+        os: [ ubuntu-latest, windows-latest ]
     steps:
     - uses: actions/checkout@v6
     - uses: ruby/setup-ruby@v1