Subdirectives are not properly indented in the TOC

Feature Overview

Some Nginx modules define new configuration blocks with a bunch of directives there, e.g. http://nginx.org/en/docs/http/ngx_http_upstream_module.html (and there many more examples in N+).

It would be helpful to see such subdirectives indented in the TOC, i.e. instead of

Directives
    upstream
    server
    zone
    state
    ...

it should be

Directives
    upstream
        server
        zone
        state
        ...

Alternatives Considered

No response

Additional Context

No response

Start by locating the documentation TOC generation entry point and inspect how directive nesting is represented for NGINX modules such as the upstream module. Confirm the current flat output and trace where parent-child relationships are available. Done means subdirectives such as server, zone, and state render indented beneath upstream in the TOC.