Exported for use by shiny::prependTab()/shiny::appendTab(). These
functions have been superseded by nav_insert() (i.e.,
shiny::insertTab()), since it can do everything these functions do (i.e.,
add a nav_panel() to the start or end of a nav_menu()) and more (i.e., insert a
nav_panel() anywhere inside a nav container).
nav_prepend(
  id,
  nav,
  menu_title,
  select = FALSE,
  session = get_current_session()
)nav_append(
  id,
  nav,
  menu_title,
  select = FALSE,
  session = get_current_session()
)
a character string used to identify the nav container.
a nav_panel() item.
The title of a nav_menu().
Should nav be selected upon being inserted?
a shiny session object (the default should almost always be used).