Add Gentoo template related

- Specific release note will follow later

QubesOS/qubes-issues#4412

os-guides/gentoo.md

@@ -0,0 +1,36 @@
+---
+layout: doc
+title: Gentoo Template
+permalink: /doc/templates/gentoo/
+---
+
+# Gentoo Template
+
+If you would like to use a stable, predictable, manageable and reproducible distribution in your AppVMs, you can install the Gentoo template, provided by Qubes in ready to use binary package.
+
+For the minimal version, please see [Minimal TemplateVMs](/doc/templates/minimal/)
+
+
+## Installation
+
+The standard Gentoo TemplateVM can be installed with the following command in dom0:
+
+    [user@dom0 ~]$ sudo qubes-dom0-update --enablerepo=qubes-templates-community qubes-template-gentoo
+
+To switch, reinstall and uninstall a Gentoo TemplateVM that is already installed in your system, see *How to [switch], [reinstall] and [uninstall]*.
+
+#### After Installing
+
+After a fresh install, we recommend to [Update the TemplateVM](/doc/software-update-vm/).
+
+## Want to contribute?
+
+*   [How can I contribute to the Qubes Project?](/doc/contributing/)
+
+*   [Guidelines for Documentation Contributors](/doc/doc-guidelines/)
+
+[switch]: /doc/templates/#switching
+[reinstall]: /doc/reinstall-template/
+[uninstall]: /doc/templates/#uninstalling
+
+