Non-interactive setup of persistent {R.cache} cache for {styler}

[lorenzwalthert]

Not sure this is relevant for your README, but for non-interactive setup, I recently realised that you can also resolve this via env variables (so it can be scripted, instead of being forced to have an interactive terminal and typing Y): https://styler.r-lib.org/reference/caching.html#non-interactive-setup. Also, apparently with my {R.cache} version (0.14), the directory does not even have to exist.

[renkun-ken]

Thanks for the information! Looks like we could update README about this.