NEW YORK—Walmart says it will start commercializing its delivery service, using contract workers, autonomous vehicles and even drones to deliver other retailers’ products directly to their customers’ homes as fast as just a few hours. Walmart will dispatch contract workers from its Spark delivery network, which was launched in 2018, to merchants’ stores to pick up items and then bring them to shoppers. Over the past year, Walmart has doubled Spark’s coverage to more than 500 cities nationwide, providing access to more than 20 million households. The nation’s largest retailer aims to tap into its ties with local communities, particularly businesses in rural areas that have struggled to implement their own delivery operations. The strategy announced Tuesday will pit Walmart against the likes of Uber, DoorDash, and other delivery services. It comes as Walmart moves to expand its sources of profits and revenues beyond its core retail businesses. It’s a …