[Twig] [Twig Reference] fix path parameter and add example in asset version function

Author: Sarah-eit

reference/twig_reference.rst

@@ -134,11 +134,30 @@ asset_version
 
 .. code-block:: twig
 
-    {{ asset_version(packageName = null) }}
+    {{ asset_version(path, packageName = null) }}
 
+``path``
+    **type**: ``string``
 ``packageName`` *(optional)*
     **type**: ``string`` | ``null`` **default**: ``null``
 
+.. code-block:: yaml
+
+    # config/packages/framework.yaml
+    framework:
+        # ...
+        assets:
+            packages:
+                foo_package:
+                    base_path: /avatars
+                    version: 'v2.0'
+
+.. code-block:: twig
+
+    {# the image lives at "public/avatars/" #}
+    {{ asset_version(path = 'avatar.png', packageName = 'foo_package') }}
+    {# output: v2.0 #}
+
 Returns the current version of the package, more information in
 :ref:`templates-link-to-assets`.