use pandoc_jll

[aviatesk]

closes #343

currently this is unfunctional, seemingly because of error in pandoc_jll side.
(upstream issue: https://github.com/JuliaBinaryWrappers/pandoc_jll.jl/issues/1)

[codecov-commenter]

Codecov Report

Merging #375 into master will increase coverage by 2.56%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master     #375      +/-   ##
==========================================
+ Coverage   71.71%   74.27%   +2.56%     
==========================================
  Files          25       25              
  Lines        1248     1244       -4     
==========================================
+ Hits          895      924      +29     
+ Misses        353      320      -33     

Flag	Coverage Δ
#unittests	74.27% <87.50%> (+2.56%)	⬆️

Impacted Files	Coverage Δ
src/writer/pandoc.jl	57.89% <85.71%> (+57.89%)	⬆️
src/rendering/htmlformats.jl	90.74% <100.00%> (+8.92%)	⬆️
src/run.jl	81.35% <0.00%> (+1.27%)	⬆️

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[rikhuijzer]

You can also use pandoc_crossref and Tectonic via Yggdrasil. I'm using both in https://github.com/rikhuijzer/Books.jl/blob/main/src/build.jl and they work fine. Feel free to copy code.

[TheCedarPrince]

Hey @pfitzseb - following up from a Slack discussion, what can I do to carry this to be successfully merged into Weave?
Is this still of interest?
I would love to see this merged as I think it would be great for the ecosystem.

[pfitzseb]

I'd recommend opening a PR against this branch that fixes CI (not sure whether pandoc_jll or Tectonic is the better choice though).