Migration to AsciiDoc: Set up initial document structure

[max-rosin]

Context

Set up the initial structure of the new documentation website, based on AsciiDoc.
This issue is part of resolving #449.

Goals

• Create initial outline of documentation to enable discussion.
• Create files to enable migration of CI to AsciiDoc early.

Tasks

• Create document map.
• Create initial document structure (files with headings only, include in map).
• Fill topics with blind text.

[stefancyliax]

This is done. Ticket closed.