Add functions to standardise system dependencies

[bschilder]

Right now there is a disconnect between the system dependencies lists in the Dockerfile and those in the rworkflows action.

rworkflows/inst/templates/Dockerfile

Line 22 in 0958123

RUN apt-get update && \

rworkflows/action.yml

Line 259 in 0958123

sysreqs=$(Rscript -e 'cat("apt-get update -y && apt-get install -y", paste(gsub("apt-get install -y ", "", remotes::system_requirements("ubuntu", "20.04")), collapse = " "))')

I could resolve this by copying-and-pasting any updates to all locations where this is relevant, or i could add some R functions to keep track the system dependencies (and what commands should be used to install them on each OS) in one place.

Thus, I've added new functions and implemented in the action and all relevant files (on the dev branch):

• New functions:
  • dependencies_linux
  • dependencies_macos
  • dependencies_windows
  • dependencies_latex