Fixed closing of dropdown for multi select

[urvashi01]

For multi-select, the menu should remain open for the user to select more options. Closing it after every selection counteracts the intuition to select multiple options.

[gwyneplaine]

thanks @urvashi01 this functionality has since been implemented in the following commit c7fe6f4
you can opt out of the default behaviour by setting the with a closeOnSelect prop to false.