old_contents: multiplesOfThreeAndFive.js
  
new_contents: // If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9.
  // The sum of these multiples is 23.
  
  // Find the sum of all the multiples of 3 or 5 below 1000.
  
subject: add desc