[UG] Explain how to enable the light/dark-mode menu (#1914)

userguide/content/en/docs/adding-content/lookandfeel.md

@@ -245,24 +245,6 @@ If the included Prism configuration is not sufficient for your requirements, and
 
 ## Navbar
 
-For pages containing a [blocks/cover][] shortcode, like most homepages, the
-navbar is translucent as long as the hero image hasn't scrolled up past the
-navbar. For an example, see the [About Docsy][] page. This initial translucent
-setting ensures that the hero image is maximally visible.
-
-After the hero image has scrolled past the navbar, the navbar's (opaque)
-background color is set -- usually to the site's [primary color][].
-
-The text of navbar entries can be difficult to read with some hero images. In
-these cases, you can disable navbar translucency by setting the
-`params.ui.navbar_translucent_over_cover_disable` option to `true` in your
-site's [configuration file][].
-
-[About Docsy]: https://www.docsy.dev/about/
-[blocks/cover]: /docs/adding-content/shortcodes/#blockscover
-[configuration file]: https://gohugo.io/getting-started/configuration/#configuration-file
-[primary color]: #site-colors
-
 ### Styling your project logo and name
 
 The default Docsy navbar (`.td-navbar`) displays your site identity, consisting
@@ -292,6 +274,64 @@ of the following:
 [wordmark]: https://en.wikipedia.org/wiki/Wordmark
 [your logo]: /docs/adding-content/iconsimages/#add-your-logo
 
+### Light/Dark mode menu
+
+If you enable this feature, Docsy adds a menu to your navbar that lets users
+switch your site's documentation page display between a default "light" mode,
+and a "dark" mode where the text is displayed in a light color on a dark
+background.
+
+To enable the display of a Light/[Dark mode] menu in the navbar, set
+`params.ui.showLightDarkModeMenu` to `true` in your project's configuration
+file. The dropdown menu appears at the right, immediately before the [search
+box], if present.
+
+{{< tabpane >}}
+{{< tab header="Configuration file:" disabled=true />}}
+{{< tab header="hugo.toml" lang="toml" >}}
+[params]
+[params.ui]
+showLightDarkModeMenu = true
+{{< /tab >}}
+{{< tab header="hugo.yaml" lang="yaml" >}}
+params:
+  ui:
+    showLightDarkModeMenu: true
+{{< /tab >}}
+{{< tab header="hugo.json" lang="json" >}}
+{
+  "params": {
+    "ui": {
+      "showLightDarkModeMenu": true
+    }
+  }
+}
+{{< /tab >}}
+{{< /tabpane >}}
+
+[dark mode]: https://getbootstrap.com/docs/5.3/customize/color-modes/#dark-mode
+[search box]: /docs/adding-content/search/
+
+### Translucent over cover images
+
+For pages containing a [blocks/cover][] shortcode, like most homepages, the
+navbar is translucent as long as the hero image hasn't scrolled up past the
+navbar. For an example, see the [About Docsy][] page. This initial translucent
+setting ensures that the hero image is maximally visible.
+
+After the hero image has scrolled past the navbar, the navbar's (opaque)
+background color is set -- usually to the site's [primary color][].
+
+The text of navbar entries can be difficult to read with some hero images. In
+these cases, you can disable navbar translucency by setting the
+`params.ui.navbar_translucent_over_cover_disable` option to `true` in your
+site's [configuration file][].
+
+[About Docsy]: https://www.docsy.dev/about/
+[blocks/cover]: /docs/adding-content/shortcodes/#blockscover
+[configuration file]: https://gohugo.io/getting-started/configuration/#configuration-file
+[primary color]: #site-colors
+
 ## Tables
 
 Docsy applies the following styles to all tables, through the class `.td-table`: