Follow up on #223 SKU Not being visible

[rhinogroup-agency]

Expected behavior

Base sku on variable product should not be required to should variant skus on the frontend. When clicking between variants it should show the sku in the sku field properly. Most companies(multi-million dollar corporations) we work with do not have base skus for configurables. At the very least this should be a setting and configurable.

Actual behavior

Currently, when a base sku does not exist on a variable product the SKU field remains empty and won't even show the variant skus.

Steps to reproduce behavior

1. Setup a product without a base SKU and add several variations with SKUs
2. Go to the PDP and toggle between the variations no SKU is shown.
3. Setup a product with a base SKU and add several variations with SKUS
4. Go to the PDP and toggle between the variations a SKU is shown properly.

Workaround or possible solution

Make this a configurable setting to be able to see this. We use BC for WordPress on lots of our sites and would like to stop having to workaround this and just have this built in. It frustrates the clients cause they are wondering why the SKU will not show. Should be a simple enough change for BC to add in.