SITES-7941: add a decoupled frontend project

[buuhuu]

Description

With this change it is possible to create an AEM SPA project that leverages the Frontend Pipeline to serve all the frontend files instead of clientlibs.

To do this a decoupled frontend module option got introduced which:

• does not create a ui.frontend maven module anymore (same as none),
• generates all the content and components like the other SPA projects (angular and react), but
• additionally adds the necessary configurations to pre-enable the Frontend Pipeline to serve the frontend code

This may be used in combination with https://github.com/adobe/aem-react-spa as a starting point for a react project that is

• editable using the SPA editor
• deployable via the Frontend Pipeline

Related Issue

SITES-7941
adobe/aem-react-spa#1
adobe/aem-spa-project-core#60

Motivation and Context

Further drive adaption of the Frontend Pipeline, in particular for SPA project.

How Has This Been Tested?

Locally

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[vladbailescu]

I think we should also provide (minimal) some instructions on how to setup the decoupled SPA project, the referenced docs don't cover this at the moment.

[buuhuu]

I think we should also provide (minimal) some instructions on how to setup the decoupled SPA project, the referenced docs don't cover this at the moment.

There are some instructions in aem-react-spa. I linked them in the Features section.