feat(menu): add menu divider

[Deliaz]

Description

In this PR I am suggesting adding Divider to the Menu component.
It is made to separate visually menu items.

In order to be displayed just need to add {divied: true} to menu items structure

const ITEMS = [
  {label: 'Menu option A'},
  {label: 'Menu option B'},
  {divider: true},
  {label: 'Menu option X'},
  ...
]

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Visual changes were detected on this branch. Please review the following PR containing updated snapshots: https://github.com/Deliaz/baseweb/pull/1