Mention targets package in README?

[joelnitta]

Prework

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Description

I just came across the targets package, and it looks great. However, it's not clear to me when I would need to stick to drake, and when I should use targets. Can this be addressed in the README? At the least, I think targets should be mentioned in the README (and probably the manual too) so users know that it is an option they should check out before committing to drake.

[wlandau]

I agree we should do this, but I would prefer to wait until targets and tarchetypes are part of rOpenSci and released to CRAN. (rOpenSci review just started: https://github.com/ropensci/software-review/issues/401.)

targets compares itself to drake in order to justify its existence, so there is detailed documentation at https://wlandau.github.io/targets/articles/need.html#drake and https://wlandau.github.io/targets-manual/index.html#what-about-drake. Briefly:

1. drake is never going away.
2. targets was necessary in order to surpass the permanent limitations of drake.
3. If you know drake, you already almost know targets.