Add menu params

Fixes #7951

docs/content/en/content-management/menus.md

@@ -113,6 +113,24 @@ This means that `.Title` will be used unless `.LinkTitle` is present, etc. In pr
 
 In this example, the top level of the menu is defined in your [site `config` file][config]. All content entries are attached to one of these entries via the `.Parent` field.
 
+## Params
+
+You can also add user-defined content to menu items via the `params` field. 
+
+A common use case is to define a custom param to add a css class to a specific menu item.
+
+{{< code-toggle file="config" >}}
+[[menu.main]]
+    name = "about hugo"
+    pre = "<i class='fa fa-heart'></i>"
+    weight = -110
+    identifier = "about"
+    url = "/about/"
+    [menu.main.params]
+      class = "highlight-menu-item"
+{{</ code-toggle >}}
+
+
 ## Render Menus
 
 See [Menu Templates](/templates/menu-templates/) for information on how to render your site menus within your templates.

docs/content/en/templates/menu-templates.md

@@ -160,3 +160,23 @@ Here's an example:
   {{ end }}
 </nav>
 ```
+
+## Using .Params in Menus
+
+User-defined content on menu items are accessible via `.Params`.
+
+Here's an example:
+
+```
+<nav class="sidebar-nav">
+  {{ range .Site.Menus.main }}
+    <a href="{{ .URL }}" title="{{ .Title }}" class="{{ with .Params.class }}{{ . }}{{ end }}">
+      {{- .Name -}}
+    </a>
+  {{ end }}
+</nav>
+```
+
+{{% note %}}
+With Menu-level .Params they can easily exist on one menu item but not another. It's recommended to access them gracefully using the [with function](/functions/with).
+{{% /note %}}