doc: Add default values to all properties

Thanks to @bojidar-bg's impressive work in #29380.

modules/visual_script/doc_classes/VisualScriptSceneNode.xml

@@ -15,7 +15,7 @@
 	<methods>
 	</methods>
 	<members>
-		<member name="node_path" type="NodePath" setter="set_node_path" getter="get_node_path">
+		<member name="node_path" type="NodePath" setter="set_node_path" getter="get_node_path" default="NodePath(&quot;.&quot;)">
 			The node's path in the scene tree.
 		</member>
 	</members>