[SideNavigationGroup] Import not required as SideNavigation automatically imports NavigationGroup

Issue Description

→ https://sap.github.io/ui5-webcomponents/components/fiori/SideNavigationGroup/

The Import for the SideNavigationGroup is implicitly imported within the SideNavigation, so an additional import is not required, see e.g. the Basic Sample (https://sap.github.io/ui5-webcomponents/components/fiori/SideNavigation/#basic-sample) which is using the NavigationGroup but does not import it.

This is currently not stated in the documentation.

It would be good to have it either clearly documented that:
a) the SideNavigationGroup is automatically imported within the SideNavigation, or
b) have the SideNavigation not implicitly import the SideNavigationGroup so that it need to be explicitly imported. (I would prefer this option as it is best practice to have all used components imported so that IDEs do not throw warnings or errors).

Issue Type

• Documentation is unclear
• Documentation is incorrect
• Documentation is missing
• Other