Create a dropdown menu to place in a dashboard header

dropdownMenu(..., type = c("messages", "notifications", "tasks"),
  badgeStatus = "primary", icon = NULL, headerText = NULL, .list = NULL)

Arguments

...	Items to put in the menu. Typically, message menus should contain `messageItem`s, notification menus should contain `notificationItem`s, and task menus should contain `taskItem`s.
type	The type of menu. Should be one of "messages", "notifications", "tasks".
badgeStatus	The status of the badge which displays the number of items in the menu. This determines the badge's color. Valid statuses are listed in validStatuses. A value of `NULL` means to not display a badge.
icon	An icon to display in the header. By default, the icon is automatically selected depending on `type`, but it can be overriden with this argument.
headerText	An optional text argument used for the header of the dropdown menu (this is only visible when the menu is expanded). If none is provided by the user, the default is "You have `x` messages," where `x` is the number of items in the menu (if the `type` is specified to be "notifications" or "tasks," the default text shows "You have `x` notifications" or "You have `x` tasks," respectively).
.list	An optional list containing items to put in the menu Same as the `...` arguments, but in list format. This can be useful when working with programmatically generated items.