Docs: Fix section for Antora: "Serials"

Docs: Fix section for Antora: "Serials"

This commit does the known tasks to prepare each main docs section for
Antora:

  - Add chapter labels to nav file items
  - (Not needed for this section.) Combine adoc files so that each
    "chapter" from the old docs structure has a single file linked from
    the nav
  - Upgrade all heading levels in each adoc file so that the top-most
    heading is a "Level 1" heading (example: "= Chapter Name =")
  - Add ":toc:" below top heading of each file

Signed-off-by: Remington Steed <rjs7@calvin.edu>