Implement a function deepMap(obj, fn) that recursively transforms all values in an object or array using the provided function.

The function should:

• Accept an object or array as the first argument.
• Accept a transformation function fn as the second argument.
• Recursively apply the function to all nested values.
• Return a new object/array without mutating the original.

Example

const obj = { a: 1, b: { c: 2, d: [3, 4] } };
const result = deepMap(obj, x => x * 2);
console.log(result); // { a: 2, b: { c: 4, d: [6, 8] } }