Add update docs

astro.config.mjs

@@ -47,6 +47,7 @@ export default defineConfig({
             { label: 'Installing as guest in QEMU/KVM', link: '/en/installation/install-guest-qemu' },
             { label: 'Installing as guest in Parallels', link: '/en/installation/install-guest-parallels' },
             { label: 'Installing as guest in UTM', link: '/en/installation/install-guest-utm' },
+            { label: 'Updating Athena OS', link: '/en/installation/update-athena' },
           ],
         },
         {

src/content/docs/en/installation/update-athena.mdx

@@ -0,0 +1,22 @@
+---
+title: Updating Athena OS
+description: How to update Athena OS.
+---
+import ImageComponent from "@components/ImageComponent.astro";
+import ThemedImage from '@components/ThemedImage.astro';
+
+Being based on Nix, the update of Athena resources needs to update the nix channel.
+
+## Update Athena OS
+
+The update process requires the update of nix channel by:
+```
+sudo nix-channel --update
+```
+This command allows the system to retrieve all the latest information about the Nix packages from Nix repository. Finally, run:
+```
+sudo nixos-rebuild switch
+```
+to update the system.
+
+<ImageComponent />