[PB-5978]: feat(sidenav)/add notification slot above storage

[jzunigax2]

Adds an optional notification prop to Sidenav, rendered between the options list and the storage section. The slot inherits the existing collapse transition so it auto-hides when the sidenav is collapsed.

[CandelR]

If the notification component is always going to be the same, apart from a few minor differences, perhaps it would be better to create it and simply pass the notification text, the button action and the button text to the sidenav itself, and if there are variations in the notification, the type as well. Because at the moment, you can pass it any type of component. What do you think?

[jzunigax2]

If the notification component is always going to be the same, apart from a few minor differences, perhaps it would be better to create it and simply pass the notification text, the button action and the button text to the sidenav itself, and if there are variations in the notification, the type as well. Because at the moment, you can pass it any type of component. What do you think?

hmm yes I believe it makes sense