Add s3 compatibility

Problem/Motivation

As currently designed, the module is not compatible with sites using s3fs → .

Steps to reproduce

N/A

Proposed resolution

Modify the imager_widget.js file to account for the possibility that a site may or may not be using s3 both locally (via a service like minio or similar) and on a dev/staging/test/production environment.

Remaining tasks

Review and test patch.

User interface changes

N/A

API changes

N/A

Data model changes

N/A