PDF using mPDF8

This is an official D8 port of the original module pdf_using_mpdf. Its used for conversion of HTML content to PDF documents using the Mpdf library.

A lot has changed in this version in terms of PDF creation. At this time, dev work is still in progress, and an alpha version is out for the curious ones:
- Developers can use Drupal Service as an API to generate PDF files. Refer README.md
- All config for the module is usable
- Only thing left is PDF generation for Drupal entities

Dependency?
Mpdf >= 7.0

Known bug:
Mpdf library does not get installed on running composer require pdf_using_mpdf8:^1.0, as a workaround you may have to run composer require 'mpdf/mpdf:^7.0' as an additional step to install the module.

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Because the maintainer of pdf_using_mpdf is unresponsive and cannot add me as a co-maintainer, this is the Drupal namespace I chose to get the D8 version. However, module namespace is still pdf_using_mpdf.

I'm following up with the correct way of Dealing with unsupported (abandoned) projects and this is taking time.