Create a function that takes a string's characters as ASCII and returns each character's hexadecimal value as a string.
toHex("hello world") ➞ "68 65 6c 6c 6f 20 77 6f 72 6c 64"
toHex("Big Boi") ➞ "42 69 67 20 42 6f 69"
toHex("Marty Poppinson") ➞ "4d 61 72 74 79 20 50 6f 70 70 69 6e 73 6f 6e"