A new Netflix documentary follows the lives of three Brooklyn sisters who were launched into the spotlight after their 2016 wins at the Junior Olympics. “Sisters on Track” centers around the Sheppard sisters: Tai, Rainn, and Brooke. They were thrust into the national spotlight in 2016 with their first-time wins in track and field at the Junior Olympics and ultimately landed on the cover of Sports Illustrated Kids as “SportsKids of the Year.” With their mother Tonia Handy, the Sheppard sisters are able to move from …