CQ-4347398 Adding Adaptive Form support in theme builder

[jalagari]

Description

AEM Forms Adaptive Form will also leverage site theme builder for building Form theme. Adding support of launching Form directly if AEM_ADAPTIVE_FORM env variables is provided.

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

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

Checklist:

• [x] I have signed the Adobe Open Source CLA.
• [x] 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.

[bartoszglow]

Hi @jalagari , please extend the readme.md file in the Environment Variables with additional variables and brief description. Apart from this PR looks fine for me.