Vegetation Components overview page is blank

[willihay]

Describe the issue

The Vegetation Components overview page contains no overview or table of subtopics.

Impacted page(s)

https://www.o3de.org/docs/user-guide/components/reference/vegetation/

Expected experience

All section pages should contain an overview of the purpose of the section and a table of subtopics, the latter of which is important for navigation on a phone.

[chanmosq]

The suggested solution for this is to include a Section topics H2 that contains a table of contents, in the order as its listed in the left-hand nav.

This solution will become standard for all component ref _index.md pages