Hey folks 
Unpkg is currently in use as a temporary mechanism for loading themes as we finalize our implementation in parallel to the early access program (EAP). It is only intended for the EAP and will only be visible in the development instances which have been enrolled into the program and not visible to your customers.
The team is actively working to remove the usage of unpkg for obvious reasons, we expect to have a solution in place within the next couple of weeks.
This is definitely a blocker for moving out of EAP, so I want to assure you that no customers will be served resources from unpkg.
Cheers,
Daniel