add "Publish to RubyGems" step

Author: GrantBirki

.github/workflows/release.yml

@@ -51,3 +51,11 @@ jobs:
           artifacts: "${{ env.GEM_NAME }}-${{ env.GEM_VERSION }}.gem"
           tag: "v${{ env.GEM_VERSION }}"
           generateReleaseNotes: true
+      
+      - name: Publish to RubyGems
+        run: |
+          mkdir -p ~/.gem
+          echo -e "---\n:rubygems_api_key: ${{ secrets.RUBYGEMS_API_KEY }}" > ~/.gem/credentials
+          chmod 0600 ~/.gem/credentials
+          gem push ${{ env.GEM_NAME }}-${{ env.GEM_VERSION }}.gem
+          rm ~/.gem/credentials