Add a simple license header that mentions the license and your name and email to the single_header file

I'm imagining that most people who use the single file header include would just like to copy it in their project (at least on a temporary basis). I'd like to make sure credit is still given in that case.

Something like this

/*
 * Copyright (c) YYYY Author <email@address>
 * 
 *  Licensed under the MIT license: https://opensource.org/licenses/MIT
 *  Permission is granted to use, copy, modify, and redistribute the work.
 *  This file is part of: https://github.com/p-ranav
 */

Adjust as you wish.