Heat coconut oil in a skillet over medium. Add chopped onion; cook 4 minutes. Add chopped mango, brown sugar, apple cider vinegar, minced garlic, minced ginger, curry powder, honey, and mustard seeds; cook 15 minutes. Transfer to a food processor; add water, unsweetened shredded coconut, and kosher salt. Pulse until combined. Stir in crushed red pepper.