By DEE-ANN DURBIN and MICHAEL LIEDTKE, AP Business WritersSAN FRANCISCO (AP) — DoorDash is expanding its offerings, adding restaurant reservations and robot deliveries in some U.S. markets. But DoorDash Co-Founder Stanley Tang said the company needs more delivery options to help fuel its future growth. DoorDash also said Tuesday it will soon begin providing some deliveries in the greater Phoenix area with an autonomous robot. Tang said DoorDash has already made hundreds of successful deliveries with Dot during the past few months in Tempe and Mesa, Arizona. If things continue to progress smoothly, DoorDash plans to bring Dot to more markets across the U.S. as quickly as possible, Tang said.