added an alternative to md2pdf(weasyprint)

[gregdrizz]

added an alternative to md2pdf, since weasy print causes a lot of trouble in different operating systems(especially windows)

pdf kit uses wkhtmltopdf as an engine which is super to install and configure on any system, from UNIX based systems to windows.

Tested and seems to be working, windows users might have to add these lines if they don't add wkhtmltopdf/bin to their PATH:

path_wkhtmltopdf = r'C:{INSTALLATION_DIRECTORY}\wkhtmltopdf\bin\wkhtmltopdf.exe' config = pdfkit.configuration(wkhtmltopdf=path_wkhtmltopdf) (won't be needed in most cases)