chore(podman): add warning about subordinate ids

knowledge base/linux/subordinate ids.md

@@ -0,0 +1,62 @@
+# Subordinate IDs
+
+> TODO
+
+Intro
+
+<!-- Remove this line to uncomment if used
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+   1. [Sources](#sources)
+
+## TL;DR
+
+<!-- Uncomment if used
+<details>
+  <summary>Setup</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Usage</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+```
+
+</details>
+-->
+
+## Further readings
+
+### Sources
+
+- [What Is the /etc/subuid File?]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+<!-- Files -->
+<!-- Upstream -->
+<!-- Others -->
+[What Is the /etc/subuid File?]: https://www.baeldung.com/linux/etc-subuid