Images are not getting displayed inside PDF (MPDF)

Think we need to add a way to log debug information from Mpdf to know why the images are not displaying.

https://mpdf.github.io/installation-setup/logging.html

$logger = \Drupal::logger('pdf_api');
$mpdf = new Mpdf\Mpdf();
$mpdf->setLogger($logger);

Yeah, I want to do a bunch of cleanups to make the whole module nicer and cleaner. Finding the time though... :)