Update README.md

README.md

@@ -339,7 +339,7 @@ function onInputKeyDown(event) {
 	Property	|	Type		|	Default		|	Description
 :-----------------------|:--------------|:--------------|:--------------------------------
 	addLabelText	|	string	|	'Add "{label}"?'	|	text to display when `allowCreate` is true
-  arrowRenderer | func | undefined | Renders a custom drop-down arrow to be shown in the right-hand side of the select: `arrowRenderer({ onMouseDown })`
+  arrowRenderer | func | undefined | Renders a custom drop-down arrow to be shown in the right-hand side of the select: `arrowRenderer({ onMouseDown, isOpen })`
 	autoBlur	|	bool | false | Blurs the input element after a selection has been made. Handy for lowering the keyboard on mobile devices
 	autofocus       |       bool    |      undefined        |  autofocus the component on mount
 	autoload 	|	bool	|	true		|	whether to auto-load the default async options set