Add documentation for non-central settings.xml updates

Our enterprise environment means we use internal repos rather than the default central repo for Maven artefacts. Because of this, we had to amend the settings.xml file with a new repository with the ID "archetype" as per https://maven.apache.org/archetype/maven-archetype-plugin/archetype-repository.html in order to resolve the artefact and create a new project.

This isn't documented anywhere in this project but given Adobe's audience, this should be a reasonably common occurrence. Adding a small "if" case with a link to the page should be enough to remind users who do not have a 'central' ID repository in-use will have to take action.

Start by checking the project's documentation around settings.xml and the Maven archetype repository guidance linked in the issue. Done means documenting the non-central repository case, including the required "archetype" repository ID and the linked reference.

Written by the indexing model from the issue text.