Update Vue docs

Author: pierredup

src/Vue/Resources/doc/index.rst

@@ -105,6 +105,7 @@ The event ``vue:before-mount`` is called before a component is mounted on the pa
 
         // Example with Vue Router
         const router = VueRouter.createRouter({
+            history: VueRouter.createWebHashHistory(),
             routes: [
                 /* ... */
             ],
@@ -113,7 +114,11 @@ The event ``vue:before-mount`` is called before a component is mounted on the pa
         app.use(router);
     });
 
-The event ``vue:before-mount`` is called when a component has been mounted on the page:
+.. note::
+   When using Vue Router, it is recommended to use "hash" (or "memory") history mode,
+   to prevent your Vue routes from being served through Symfony controllers.
+
+The event ``vue:mount`` is called when a component has been mounted on the page:
 
 .. code-block:: js