[Exp] Add native stack follow-up demo

[skip ci]

Author: hujc7

.github/native-stack-demo/followup.md

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+<!--
+Copyright (c) 2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+All rights reserved.
+
+SPDX-License-Identifier: BSD-3-Clause
+-->
+
+# Native stack demo: follow-up
+
+This file belongs only to the top layer of the disposable GitHub stacked-pull-request demo.