Document changes to configuration

[wlandau]

Prework

• Read and agree to the code of conduct and contributing guidelines.
• If there is already a relevant issue, whether open or closed, comment on the existing thread instead of posting a new issue.
• For any problems you identify, post a minimal reproducible example like this one so the maintainer can troubleshoot. A reproducible example is:
  • Runnable: post enough R code and data so any onlooker can create the error on their own computer.
  • Minimal: reduce runtime wherever possible and remove complicated details that are irrelevant to the issue at hand.
  • Readable: format your code according to the tidyverse style guide.

Description

• Configurable target script file path: Configurable target script path ropensci/targets#480
• Target Markdown script path: Set location of output script files in Target Markdown ropensci/targets#478