add pipeline output for debugging

Author: KrisSimon

.github/workflows/builds-mattermost.yaml

@@ -59,6 +59,8 @@ jobs:
       - name: Read Content
         id: getcontent
         run: echo "::set-output name=payload::$(cat mattermost.json)"
+      - name: Pipeline Output
+        run: echo "${{ steps.getcontent.outputs.payload }}"
       - name: Send Mattermost Message
         uses: mattermost/action-mattermost-notify@master
         with: