BEST GINGER CARROT SOUP

1 tablespoon extra-virgin olive oil ½ medium yellow onion, chopped ½ teaspoon sea salt 3 garlic cloves, smashed 1 pound carrots, roughly chopped 1 teaspoon grated fresh ginger 1 tablespoon apple cider vinegar 3 cups vegetable broth Freshly ground black pepper 1 teaspoon maple syrup, optional Coconut milk, for garnish, optional