Add modern way of loading initial-state

Signed-off-by: Louis Chemineau <louis@chmn.me>

developer_manual/basics/front-end/js.rst

@@ -109,7 +109,7 @@ and a JS part (that fetches and parses the state).
 
 Providing the initial state with PHP
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Providing state in PHP is done via the ``\OCP\IInitialStateService``. This service
+Providing state in PHP is done via the ``OCP\AppFramework\Services\IInitialState``. This service
 has two methods you can use to provide the initial state.
 
 * ``provideInitialState(string $appName, string $key, $data)``:
@@ -130,6 +130,19 @@ Obtaining the initial state in JavaScript
 To obtain the initial state in your JavaScript you have to only call one
 function
 
+- Vue way with `@nextcloud/initial-state <https://github.com/nextcloud/nextcloud-initial-state>`_:
+
+.. code-block:: js
+
+    import { loadState } from '@nextcloud/initial-state'
+
+    const val = loadState('myapp', 'user_preference')
+
+    // Provide a fallback value to return when the state is not found
+    const valWithFallback = loadState('myapp', 'user_preference', 'no_preference')
+
+- Legacy way:
+
 .. code-block:: js
 
     const state = OCP.InitialState.loadState('MyApp', 'MyState');