docs(user-settings): update README for new frontend system as default

Move old frontend system wiring instructions to an "Old Frontend
System" section. The default installation path now uses package
discovery with no manual wiring needed.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

plugins/user-settings/README.md

@@ -11,7 +11,20 @@ be used in the frontend as a persistent alternative to the builtin `WebStorage`.
 Please see [the backend README](https://github.com/backstage/backstage/tree/master/plugins/user-settings-backend)
 for installation instructions.
 
-## Components Usage
+## Installation
+
+```bash
+# From your Backstage root directory
+yarn --cwd packages/app add @backstage/plugin-user-settings
+```
+
+Once installed, the plugin is automatically available in your app through the default package discovery. For more details and alternative installation methods, see [installing plugins](https://backstage.io/docs/frontend-system/building-apps/installing-plugins).
+
+## Old Frontend System
+
+If your Backstage app uses the old frontend system, you need to manually wire the plugin into your app.
+
+### Components Usage
 
 Add the item to the Sidebar: