sideNav - examples for expanding active subsections and highlighting current section

[gordongrace]

Feature Request

• [ ] I’ve read and understood the Contributing guidelines and have done my best effort to follow them.
• [ ] I’ve read and agree to the Code of Conduct.
• [ ] I’ve searched for any related issues and avoided creating a duplicate issue.
• [ ] I've searched the community forums to check for related issues or feature requests

Is this feature request relating to an existing component? Please describe.

• Component name: side-nav
• Component version: 5.07

Do you have a suggestion for a new component?

Tips/guidance for this component state:

Only expand active subsections to help emphasise which section the user is in and to reduce visual complexity.

Are there options worth exploring to:

1. Provide stronger visual/semantic emphasis on the current page/section a user is in (highlighting, emboldening, other indicators)
2. Demonstrate how to only expand (client-side/server side) the section a user is in (current examples show two sibling sections expanded)

Additional context

Implementation of sidenav by health.gov.au (example at https://www.health.gov.au/about-us/corporate-reporting/budgets) provides alternative ideas for highlighting current section.

[sukhrajghuman]

also relates to #549