Update decoupled menus documentation

Problem/Motivation

The format of the linkset has changed recently. The documentation needs a runtrough, but mostly, the example → needs updating.

Steps to reproduce

n.a.

Proposed resolution

Update docs.

Remaining tasks

Update docs.
Make any necessary changes to the core Menu API → docs.

User interface changes

n.a.

API changes

n.a.

Data model changes

n.a.

Release notes snippet

n.a.