Update for PHP 8

[aaronpk]

The fpdf library doesn't support php 8

[austinginder]

Hope you don't mind, I forked your project for a different purpose 😄 . In my fork I was able to upgrade FPDF to the latest using composer composer require fpdf/fpdf. Then a few other tweaks to more or less keep the rest of the code as-is. Feel free to look over my code if helpful.