chore(kb): start article about update-alternatives

knowledge base/update-alternatives.md

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+# `update-alternatives`
+
+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>Installation and configuration</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<details>
+  <summary>Usage</summary>
+
+```sh
+# Get configured alternatives and their values.
+update-alternatives --get-selections
+
+# Show the full list of alternatives for commands.
+update-alternatives --display 'java'
+
+# *Interactively* change the default alternative for commands.
+update-alternatives --config 'java'
+update-alternatives --config --all
+```
+
+</details>
+
+<!-- Uncomment if used
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+```
+
+</details>
+-->
+
+## Further readings
+
+### Sources
+
+- [`update-alternatives`: managing multiple versions of commands and files][update-alternatives: managing multiple versions of commands and files]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+<!-- Files -->
+<!-- Upstream -->
+<!-- Others -->
+[update-alternatives: managing multiple versions of commands and files]: https://documentation.suse.com/sles/15-SP5/html/SLES-all/cha-update-alternative.html