chore(kb/netcat): revise article, split by userland

knowledge base/gnu userland/netcat.md

@@ -0,0 +1,59 @@
+# Netcat
+
+> TODO
+
+Intro
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
+## TL;DR
+
+<details>
+  <summary>Setup</summary>
+
+```sh
+brew install 'netcat'
+```
+
+</details>
+
+<details>
+  <summary>Usage</summary>
+
+```sh
+# Listen (server mode).
+netcat --listen --local-port '8080'
+nc -lp '8080'
+```
+
+</details>
+
+<!-- Uncomment if used
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+```
+
+</details>
+-->
+
+## Further readings
+
+- [Website]
+- [Codebase]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+<!-- Files -->
+<!-- Upstream -->
+[Codebase]: https://sourceforge.net/p/netcat/code/HEAD/tree/
+[Website]: https://netcat.sourceforge.net/
+
+<!-- Others -->