nav: right CONTENT sidebar highlights 2nd header on top window position

[jorgeorpinel]

Right-side CONTENTS element doesn't highlight the right header, at least with scroll 0 in the example below:

https://dvc.org/doc/install/macos

[jorgeorpinel]

Also related/ part of the solution: #37

[iKBAHT]

Some ideas:
https://github.com/iterative/dvc.org/blob/master/src/components/Documentation/RightPanel/index.tsx#L44
A peculiarity of the navigation algorithm

[jorgeorpinel]

Ping @iterative/websites small bug outstanding here.

Also related: #37

[jorgeorpinel]

p.s. this only happens in pages with an H2 near the top (most). Otherwise nothing is highlighted (see also #37), e.g. for https://dvc.org/doc/user-guide/experiment-management/sharing-experiments (in my screen at least).

[jorgeorpinel]

Hmmm. This may be a more general issue. For example https://dvc.org/doc/command-reference/plots#html-templates highlights the next header as well:

[rogermparent]

We can probably overhaul the highlighting logic using intersection observers and some more elegant plumbing on getting the headers in the list synchronized with the content.