Add support for AWS lambda

[emmanuel2804]

In order to use wkhtmltopdf in a lambda it is necessary to add the binary files in a layer, these files are in the $PATH variable of the system. PATH = /var/lang/bin:/usr/local/bin:/usr/bin/:/bin:/opt/bin Files: /opt/bin/wkhtmltoimage /opt/bin/wkhtmltopdf

When I try to use var converter = new HtmlConverter(); that throw a exception because wkhtmltoimage is not installed on that linux system.