doc: search indicators missing

[eljefedelrodeodeljefe]

• Version: all
• Platform: all (likely, confirmed Safari, Chrome on OS X)
• Subsystem: doc

As described in #6479 at the bottom, search indicators in browsers are missing which probably was unintentional:

Chrome (at least on a Mac) will give you indicators on the scrollbar of where cmd+f results are. Using custom styles on the scrollbar breaks this – so I'm glad to see it works again in the narrow view. However, in the wide view, since the content area's scrollbars are not on the body, they still don't work there:

[ChALkeR]

This could be fixed by using position: fixed on the menu and making the right part the actual contents without a separate scrollbar, but using the body scrollbar instead

[silverwind]

Sounds like soemthing like #5716 could fix this. I'll see if I can satisfy all cases.