Place the salsa, taco seasoning, lime juice, and cilantro into a slow cooker, and stir to combine. Add the chicken breasts, and stir to coat with the salsa mixture. Cover the cooker, set to High, and cook until the chicken is very tender, about 4 hours. If desired, set cooker to Low and cook 6 to 8 hours. Shred chicken with 2 forks to serve.