Stay aware of electron `printToPDF` improvements, to get rid of print background hack

[etpinard]

See #6 (review) and #6 (comment) for more details.

[etpinard]

Interesting. this url-to-pdf-api package has a pdf.pageRange option listed under:

https://github.com/alvarcarto/url-to-pdf-api#get-apirender

which would make setBackground from #6 hack obsolete.