Healthy Grilled Shrimp Fajita Foil Pack

Name: Healthy Grilled Shrimp Fajita Foil Pack
Ingredients: 2 large bell peppers, sliced 1/2-inch thick; 1 large onion, sliced 1/2-inch thick; 1 bunch scallions, quartered crosswise; 2 tablespoons olive oil; 1/2 teaspoon chipotle chile powder; 1/2 teaspoon ground cumin; Kosher salt; 1 1/4 pounds extra-large peeled and deveined shrimp, tails removed; 2 limes, halved; Twelve 6-inch flour tortillas; 1/2 cup loosely packed cilantro leaves and tender stems; Salsa and chopped avocado for serving, optional