Sophie Byroade was scrolling on Facebook last summer when she stumbled on an unusual post: It was from a mother looking for a liver donor for her sick three-year-old son. “Nolan needs a liver hero,” it read. The post described Nolan Smith as a “sweet, dinosaur-loving, music-dancing, water-splashing” child –– all things that reminded Byroade of her five-year-old sister. The Jacksonville preschooler, who has a rare and serious liver condition, had…