Update pdf.css with new workshop style

[Shrinks99]

pdf.css should be brought in line with the new workshop style.

• New typography
• Update a mesh graphics used in PDFs
• New style for in-line and blocks of code

All content is intended for printing in black and white but colour can still be used here and there as long as enough contrast is provided.

[Shrinks99]

This is proving to be a little trickier than expected, markdown-pdf does not seem to support the font-weight CSS property and this is a huge typographical bummer. Until this is fixed I am unable to update pdf.css to match the new font choices and it's actually a miracle that my 10 minutes of untested code works as well as it does.

[Shrinks99]

@benhylau Because of the flaws in markdown-pdf (and the fact that it looks like they're not getting fixed any time soon we may want to have a look at mdpdf instead. It seems to work in almost exactly the same way but is also a bit more fully featured.

[benhylau]

Will looK!