How to open and close all SubMenu items for inline?

[Gervwyk]

It would be great to have a flag to open and close all submenu items for inline menu. Is this possible? Or just set a prop on SubMenu that it is open / expanded. Managing the state list of openKeys can create various bugs. Perhaps we can map isOpen as a external prop also? https://github.com/react-component/menu/blob/353039be098cd2c65593c7f8217428bb3e872df0/src/SubMenu.jsx#L553