[action] send notificatioin if update container images job failed

.github/workflows/update-image-digest.yml

@@ -109,3 +109,15 @@ jobs:
           labels: automated pr, kind/cleanup, release-note-none
           branch: update-digests
           delete-branch: true
+
+      - name: Get previous job's status
+        id: lastrun
+        uses: filiptronicek/get-last-job-status@main
+      - name: Slack Notification
+        if: ${{ (success() && steps.lastrun.outputs.status == 'failed') || failure() }}
+        uses: rtCamp/action-slack-notify@v2
+        env:
+          SLACK_WEBHOOK: ${{ secrets.WORKSPACE_SLACK_WEBHOOK }}
+          SLACK_COLOR: ${{ job.status }}
+          SLACK_TITLE: "Update container images digest"
+          SLACK_FOOTER: "<https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}|Workflow logs>"