Components which can't be used in isolation shouldn't be shown out of context

[greatislander]

Describe the bug

As reported in #323, some components which are currently displayed in the component library don't function as expected when not in the appropriate context (the menu component needs to be within the banner and appropriately wrapped in containing elements for the mobile layout to work as expected, for example).

These components, which are not intended to be used out of context, should be hidden (their directories should be named with a _ prefix).

To Reproduce

See issues reported in #323.

Expected behavior

This component should not be shown in isolation.

Additional Context

https://fractal.build/guide/core-concepts/naming.html#ordering-and-hiding