workflow/publish: fix publish to github

Author: gi

.github/workflows/publish.yml

@@ -25,6 +25,7 @@ jobs:
       - name: Publish to GitHub
         env:
           GEM_HOST_API_KEY: "Bearer ${{secrets.GITHUB_TOKEN}}"
+          RUBYGEMS_HOST: https://rubygems.pkg.github.com/${{github.repository_owner}}
         run: bin/release
   rubygems:
     name: RubyGems