ST. LOUIS — The American Red Cross has an urgent need for donors and is counting on people to act now and book a time to give blood or platelets. Donors of all blood types and those giving platelets are needed to keep a strong supply of lifesaving blood products on hospital shelves into the summer. As summer heat ramps up, so do people’s plans, which could lead to postponed appointments or less opportunities to give - an especially troubling sce…