Document optional Pandoc packages

[fkohrt]

Pandoc's default LaTeX template is clever: Some packages–as of v2.14.1 "upquote", "microtype", "parskip", "xurl", "bookmark" and "footnotehyper"–will only be used if they are available (checked via \IfFileExists). This way, however, they don't raise LaTeX error messages and tinytex::parse_packages() won't detect them.

Maybe the fact that optional packages won't be installed by the tinytex package should be documented somewhere? I am not sure where exactly this should go, mabye it's better suited in the tinytex documentation. Another option would be adding the packages in question to the extended TinyTeX release. (Or is there some other way that tinytex can actually detect these optional dependencies?)