Add sub-doc as interlink automatically at creation

[virgile-dev]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.
A lot of parent docs tend to be empty, making navigation hard for users.

Describe the solution you'd like

• When a subdoc is created with the sidebar, an interlink appends at the end of the parent doc.
• When a user user user the /new sub-doc command an interlink is created where the user triggered the command

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Discovery, Documentation, Adoption, Migration Strategy
If you can, explain how users will be able to use this and possibly write out some documentation (if applicable).
Maybe add a screenshot or design?

Do you want to work on it through a Pull Request?