Looks for a file named _projthis.yml in path_proj. If present, reads
using yaml::read_yaml(); if not present, returns NULL.
proj_workflow_config(path_proj)character path to workflow directory,
relative to the project directory.
NULL, or list describing workflow configuration
The configuration supports a single element, render.
render:
first:
00-import.Rmd
last:
99-publish.Rmd