Add a page about Artefactual

On the Internet, [every page is page on](https://everypageispageone.com/the-book/).

If this was your first time stumbling upon the Portal, and you wanted to know more about Artefactual, where would you go?

Read the linked Every Page Is Page One guidance for context, then inspect the Portal's existing page structure and navigation. The issue names no file, entry point, test, or acceptance criteria; completion would require deciding where an Artefactual page belongs and agreeing on its newcomer-oriented content.

Written by the indexing model from the issue text.