feat: set the CWD for pandoc to the input dir

[janLo]

This sets the working directory of pandoc to teh directory the source file lives in. This makes it easier to use resources located relative to the input file.

An example is a logo reference in a frontmatter block for a pandoc template (like the eisvogel template).

[arne-kapell]

I would love to see this merged as I want to use a relative path for the *.bib in citations 😄

[OliverBalfour]

Apologies this took so long! It's just been merged in 4.0