Render for correct output in weigh()

[juliasilge]

Addresses #280

I used rmarkdown::render() directly here, after building the package locally. I am very mystified about what might be going on here!

[juliasilge]

This is the substantive change, i.e. the current wrong output being shown in our rendered README.

[simonpcouch]

Thanks for the callout!

[simonpcouch]

This is sooo strange and I also don't have a good sense of what's happening here!🫣

I imagined my 6-months-from-now-self would likely devtools::build_readme() without thinking about it, so I wondered if we could detect when we're evaluating inside of that function and error in that case. This bit of code in the setup chunk appears to do the trick, in case you're inclined:

# `devtools::build_readme()` evaluates in `callr:r_safe()` which causes issues
# with butcher's memory profiling. Neither RStudio's Knit button nor
# `rmarkdown::render()` have this issue (#280).
if (identical(Sys.getenv("CALLR_IS_RUNNING"), "true")) {
  rlang::abort(c(
    "Build this README with `rmarkdown::render()` rather than `devtools::build_readme()`.",
    "See tidymodels/butcher#280 for more info."
  ))
}