[infra] Add closing message workflow (#43450)

.github/workflows/closed-issue-message.yml

@@ -0,0 +1,18 @@
+name: Add closing message to issue
+
+on:
+  issues:
+    types:
+      - closed
+  workflow_call:
+
+permissions: {}
+
+jobs:
+  add-comment:
+    name: Add closing message
+    if: github.event.issue.state_reason == 'completed'
+    uses: mui/mui-public/.github/workflows/reusable/add-closing-message-to-issue.yml@04275a99fe10cee127ee417b8a872cfebc7d08e7
+    permissions:
+      contents: read
+      issues: write

.github/workflows/support-stackoverflow.yml

@@ -32,4 +32,5 @@ jobs:
             If you have a question on Stack Overflow, you are welcome to link to it here, it might help others.
             If your issue is subsequently confirmed as a bug, and the report follows the issue template, it can be reopened.
           close-issue: true
+          issue-close-reason: 'not planned'
           lock-issue: false