Support nested menu items with its own contents in PagesPlugin?

[roll]

Overview

Currently, it's only possible to create a nested menu item in the PagePlugin as a container. It will not be associated with any page. This behavior is the same as Docusarus has for example. We can think of allowing both:

• virtual nested menu element
• nested menu element with its own contents

Example

pages:
  items:
    # ...
    - name: Getting Started
      path: docs/getting-started # not supported currently
      items:
        - name: Installation
          path: docs/installation
        - name: Configuration
          path: docs/configuration