Side-nav improvements

[spartanatreyu]

Currently, the user needs to keep scrolling to the top of the page to see the side-navigation before they can use it.

Since there is already space for the navigation on the side, we could stick the side-navigation easily enough so the user can have a smoother navigation experience.

It might also be possible to use intersection observers to highlight which sections of the navigation the user is currently viewing. Here is a blog post talking about this: https://www.smashingmagazine.com/2021/07/dynamic-header-intersection-observer/

[lamiazar]

Thank you @spartanatreyu, I was just about to open an issue about that.
This is a good enhancement to add.cc @heapwolf @chicoxyzzy