Promisifying Callback-based Asynchronous Functions (Challenge)

# Introduction

In this challenge, we will be working with JavaScript to encapsulate a `promisify` function. The purpose of this lab is to convert the callback-style file reading method in Node.js into a Promise version. By completing the code in the `index.js` file, we will be able to convert the `readFile` method in `fs` to a Promisified version that can be utilized with the `then` method to execute the success or failure callbacks.