Update README.md

Author: CodeWithDennis

README.md

@@ -62,6 +62,9 @@ SelectTree::make('category_id')
 // Expand the tree with selected values
 ->expandSelected(false)
 
+//	All groups will be opened to this level
+->defaultOpenLevel(2)
+
 // Display individual leaf nodes instead of the main group when all leaf nodes are selected
 ->grouped(false)