chore(github): add closed issue workflow

.github/workflows/closed-issue.yml

@@ -0,0 +1,21 @@
+name: Closed issue
+on:
+  issues:
+    types: [closed]
+
+jobs:
+  comment:
+    permissions:
+      issues: write
+    runs-on: ubuntu-latest
+    steps:
+      - uses: peter-evans/create-or-update-comment@v4
+        with:
+          token: ${{ github.token }}
+          issue-number: ${{ github.event.pull_request.number }}
+          body: |
+            Closed issues are **NOT** monitored, so commenting here is likely to be not seen.
+            If you think this is *still unresolved* and have **more information** to bring, please create another issue.
+
+            This is an automated comment setup because @qdm12 is the sole maintainer of this project
+            which became too popular to monitor issues closed.