Create a function that calculates the profit margin given costPrice and salesPrice. Return the result as a percentage formatted string, and rounded to one decimal. To calculate profit margin you subtract the cost from the sales price, then divide by sales price.
profitMargin(50, 50) ➞ "0.0%"
profitMargin(28, 39) ➞ "28.2%"
profitMargin(33, 84) ➞ "60.7%"