feat(client/textui): add text return to isTextUIOpen (#464)

resource/interface/client/textui.lua

@@ -35,7 +35,7 @@ function lib.hideTextUI()
     currentText = nil
 end
 
----@return boolean
+---@return boolean, string | nil
 function lib.isTextUIOpen()
-    return isOpen
-end
+    return isOpen, currentText
+end