CEXT-5882-pruned readme and added link to public docs

[nofuss]

Description

This is a follow up to AdobeDocs/app-builder#488 where the content in this README was merged into the public developer docs at https://developer.adobe.com/app-builder/docs/guides/app_builder_guides/storage/database

https://jira.corp.adobe.com/browse/CEXT-5882

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)
• 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.