Add RubyGems credentials configuration step

Author: kateinoigakukun

.github/workflows/build-gems.yml

@@ -97,5 +97,6 @@ jobs:
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: "3.4"
+      - uses: rubygems/configure-rubygems-credentials@v1.0.0
       - run: gem build
       - run: gem push ruby_wasm-*.gem