Solve: Validate Username 1

Created By: Justin Maier

/ Version: 2024.8.0

Write a function validUsername that takes two arguments: a String representing a new username and a String array of saved usernames.

For a username to be valid, it must be between 5 and 18 characters long, inclusive. Additionally, it must not be in the list of saved usernames.

Your function should return whether the new username is valid.