Apple is adding an additional incentive for Apple Store customers in the U.S. and U.K. to activate Apple Pay by offering a $5/£5 iTunes Gift Card, according to a new report by Macrumors. Customers making an in-store purchase will be asked by Apple Store staff whether they will be paying with Apple Pay, and customers who do not already have Apple Pay set up on their iPhones and wish to do so will be taken through the process by the Apple Store employee…