Basket State Improvements

When a product/contract is being added to basket, we are updating an array of IDs now, in the basket module's state called productIdsBeingAdded: (string | number)[].

When a product/contract is being removed from basket, we are updating an array of IDs now, in the basket module's state called productIdsBeingRemoved: (string | number)[].

This may come in handy if you want to take some actions when a particular product/contract is being added to/removed from basket, via the onChange listener.