feat: Add proof of concept docs site BM-917

[ajacombs]

Motivation

This adds an initial proof of concept of a documentation site. The documentation is generated from a combination of static Markdown documents; currently lightly modified from the existing files, plus a few placeholders.

API documentation is generated from the typescript source code using Typedoc. This is rendered to Markdown files using typedoc-plugin-markdown, which is combined with the static Markdown files to render the documentation site using MkDocs.

Modification

This is a rough proof of concept implementation, to be fleshed out in subsequent PRs which will:

• Add more documentation.
• Improve the readability of the generated API docs (fix typographic hierarchy and character escaping issues).
• Update the theme to match LINZ branding.

Checklist

• Tests updated
• Docs updated
• Issue linked in Title