Add RBAC example

fern/products/docs/pages/authentication/rbac.mdx

@@ -4,7 +4,6 @@ subtitle: Control who can view your documentation
 description: Learn how to restrict access to your documentation using role-based access control (RBAC)
 ---
 
-
 <Warning title="Team and Enterprise feature">
   Password-based RBAC is available on the [Team and Enterprise plans](https://buildwithfern.com/pricing). JWT and OAuth-based RBAC require the [Enterprise plan](https://buildwithfern.com/pricing).
 </Warning>
@@ -77,6 +76,30 @@ Use the `<If />` component to [conditionally render content](/learn/docs/writing
 
 You can also combine `roles` with `products` and `versions` props.
 
+## Example
+
+Fern's RBAC demo site defines the following roles:
+
+```yml docs.yml
+roles:
+  - everyone
+  - work-trial
+  - engineers
+  - contractors
+```
+
+Unauthenticated users can only access sections marked as `viewers: everyone`. After logging in, users with the `work-trial`, `engineers`, or `contractors` role can access work trial content, engineering documentation, and contractor information.
+
+<Frame caption="The `docs.yml` defines roles and gates sections, then the [live site](https://engineering.ferndocs.com/rbac-demo/public-content/) shows the public view.">
+  <video
+    autoPlay
+    muted
+    loop
+  >
+    <source src="assets/rbac.mp4" type="video/mp4" />
+  </video>
+</Frame>
+
 <llms-only>
 ## Common errors