Enable Proofing in Sandboxes

[#1]

We relly heavily in Proofing and the proofing custom form.

We have multiple automated templates and fields that we capture. When we need to add new proofing fields, automated templates or make updates or changes to existing ones, having only Preview to test and demo those changes makes it very difficult for us as one week is not enough time to have demo and uat for all the required stakeholders.

Some of our automated templates can have up to 20 stages so recreating this every week in Preview is very cumbersome and inefficient. 

We would like to have Proofing available in the Sandbox environments.