Feature/39 - Content authors can write contents of index

• The same component (`Article.astro`) is responsible for rendering any markdown article, including home

• The home article is published to index.html, meaning it will appear on ecobytes.net/

• On directus, there is exactly one item called Home.

  The data structure on directus mirrors the other markdown collections, except that unit fields (title, sort, slug, id) that can't be changed are readonly and hidden, and that the whole collection is a singleton, meaning there is always exactly one instance of the schema.

• Content authors get the same interface as for the other pages, minus slug and title as these are units (both are "")

• @yala has implemented a "system" collection of text files for SEO and config purposes. It is already downloaded as part of the build process but not yet written into files (-> new issue)

Closes #39 (closed)