ui: stark-app-menu keep highlight when navigating from Parent Page to child pages (sub pages)

[Robin Giel]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Current behavior

When navigating from a parent page to a child page, we lose the highlight in the menu

Expected behavior

When navigating from a parent page to a child page (sub pages) we keep the highlight in the menu.

What is the motivation / use case for changing the behavior?

Better user experience