refactor: replace slow performing CSS selectors

[mfranzke]

Proposed changes

Resolves #2967

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (fix on existing components or architectural decisions)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Further comments

[github-actions]

🔭🐙🐈 Test this branch here: https://db-ui.github.io/mono/review/2967-slow-performance-css-selectors

[bruno-sch]

This would certainly improve performance. Unfortunately, through this change NavigationItems are no longer marked as active if a nested NavigationItem has aria-current=“page”. From a11y point of view, we recommend that you only set aria-current=“page” to the anchor that points to the current page.

An alternative would be to use JS to set an “active” class from the innermost active NavigationItem to the outermost NavigationItem. But is that better than using the has-selector...?

[mfranzke]

I think to remember that this wasn't even only about line 84 within the original file, but especially about the upfollowing 88 till 96, that even also provided a concatenated :has selector. I'll further investigate on this one.