feat: Add additional job to trigger slack notification

Author: lamATnginx

.github/workflows/build-push.yml

@@ -73,6 +73,25 @@ jobs:
       AZURE_CREDENTIALS: ${{secrets.AZURE_CREDENTIALS_DOCS}}
       AZURE_KEY_VAULT: ${{secrets.AZURE_KEY_VAULT_DOCS}}
 
+  trigger-theme-slack-notification:
+    if: github.event_name == 'repository_dispatch'
+    needs: call-docs-build-push
+    runs-on: ubuntu-latest
+    steps:
+      - name: Trigger 'Slack notification for new theme release' workflow in 'nginx-hugo-theme' repo.
+        run: |
+           event_type="trigger-slack-notification" 
+           curl -L \
+              -X POST \
+              -H "Accept: application/vnd.github+json" \
+              -H "Authorization: Bearer ${{ secrets.PERSONAL_ACCESS_TOKEN }}" \
+              -H "X-GitHub-Api-Version: 2022-11-28" \
+              "https://api.github.com/repos/nginxinc/nginx-hugo-theme/dispatches"
+              -d "{\"event_type\": \"$event_type\", \"client_payload\": {\"previewURL\": \"${{PREVIEW_URL}}\"}}"
+    env:
+      PREVIEW_URL: ${{ needs.call-docs-build-push.outputs.PREVIEW_URL }}
+
+
   lighthouseci:
     if: github.event.pull_request
     needs: call-docs-build-push