By Veronika Bondarenko Popeyes President Sami Siddiqui talked with TheStreet about how new items hit the menu, about plant-based trends, robots and international expansion. While fast-food chains like to talk about expansion plans and digital subscriptions, the questions that many of their customers want answered are: “How is that made?” and “What’s coming to the menu next?” Certain fans meticulously track any changes to their favorite chains’ menus. But the process of going from idea to menu item often remains shrouded because competition is sharp and restaurants don’t want to give rivals an …