Type-safe props in AppShell and AppHeader

[filipjnc]

Describe the feature request
Currently, the AppShell and AppHeader don't have types defined for following props:

  @Prop() mainNavigation?: any = [];
  @Prop() iconNavigation?: any = [];
  @Prop() userNavigation?: any = [];
  @Prop() sectorNavigation?: any = [];
  @Prop() addonNavigation?: any = [];

Describe the use case
I would like type safety when passing the prop values to these components.