ci deploy: release add deploy workflow to notify successful package u…

…pload

GitHub: groonga/packages.groonga.org#43

This PR introduces a new Deploy workflow that triggers upon the
completion of uploading packages.

The Deploy workflow is responsible for handling deployment flows in
near future.

At first step, we will trigger the webhook using this workflow to
sign packages and upload them. Please refer the issue in detail.

.github/workflows/deploy.yml

@@ -0,0 +1,16 @@
+name: Deploy
+on:
+  push:
+    tags:
+    - '*'
+  workflow_run:
+    workflows: ["Package"]
+    types:
+      - completed
+jobs:
+  notify:
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Notify successful package upload
+        run: echo "Package upload has been successfully completed."