Support header comments in sidebar

[thetic]

Requested feature:

I love the sidebar introduced in 2.13. I think there is some room to make it even better.

I tend to group related configuration section in groups:

It would be great if the sidebar were able to interpret comments like these to add another level of hierarchy instead of showing a flat list of configuration sections.

There's probably a better syntax to indicate a group header comment; I'm open to anything.

Solves the following problem:

This would make the sidebar even more helpful in navigating a config.

Additional information:

No response