add types to arrowfunction js code example

Example 1: es6 arrow function

const multiplyES6 = (x, y) => x * y;

Example 2: Arrow Functions

// The usual way of writing function
const magic = function() {
  return new Date();
};

// Arrow function syntax is used to rewrite the function
const magic = () => {
  return new Date();
};
//or
const magic = () => new Date();