Add support to the Project Archetype for the Email Core Components

As an additional Archetype option, in addition to creating a regular site - meaning that the email components won't allow to be created in stand-alone.

Start by locating the Project Archetype entry point and its existing regular-site generation path. Clarify how an additional archetype option should enable creation of the Email Core Components, then add coverage for that option and verify the generated project includes them.

Written by the indexing model from the issue text.