Few protagonists are more compelling than the underdog sports hero, and “Strider” adds a new icon to the cinematic pantheon, upholding the grand tradition of “Rudy,” “Hoosiers,” and “Million Dollar Baby.” Jody (Yelena Friedman), a lonely teenage girl, joins forces with Hannah (Maggie Alexander), a disgraced track coach, and together they spend a summer training for the Pinnacle Games, the biggest track-and-field competition on the East Coast. An irresistibly inspiring indie, “Strider” is likely to have audiences cheering loudly in support as Jody and Hannah attempt to run down their mutual dream.