Left nav issues

[eric-schneider]

There are two major issues with the left nav.

Parent nav items can't be links

The UI currently doesn't support the following nav configuration:

* xref:parent-page.adoc[]
** xref:child-page.adoc[]

The parent page doesn't present as a link. This has forced us to use an undesirable workaround of making the parent page a child of itself, for example:

* Parent page
** xref:parent-page.adoc[]
** xref:child-page.adoc[]

A list title is required

IMPORTANT: As @mlr pointed out below, this should be fixed as of #103.

Currently, the UI requires the nav to have at least one list title element, otherwise it won't render anything at all.

✅ Does render

.Some title
* xref:page-1.adoc
* xref:page-2.adoc
* xref:page-3.adoc
* xref:page-4.adoc

❌ Does not render

* xref:page-1.adoc
* xref:page-2.adoc
* xref:page-3.adoc
* xref:page-4.adoc

Some products don't have enough pages to warrant using list titles. However, we've had to add at least one so that nav will at least show the pages in the first place:

[mlr]

A list title is required
Currently, the UI requires the nav to have at least one list title element, otherwise it won't render anything at all.

A list title shouldn't be required anymore as of #103

See the streaming doc sub sites as an example of this. We still render the links, they just don't have a title or parent drop down.

Example: https://docs-stage.datastax.com/en/streaming/index.html
Relevant nav: https://raw.githubusercontent.com/DataStaxDocs/datastax-streaming-docs-site/main/site-main/modules/ROOT/nav.adoc