add whitelists

[dmi3kno]

I implemented whitelists in options that are loaded onLoad.
The whitelists are extensible via options("rbbt.whitelist.user"=c()).

The vector whitelists are converted to regex in internal function and then excluded from the vector of keyes using the str_subset as you suggested.

[paleolimbot]

I don't have the ability to test this anymore but am happy to merge this if it makes anybody's life easier. From a design perspective I think setting options in .onLoad() could lead to unexpected behaviour and should be avoided...probably just the ability to add a whitelist_quarto = TRUE or a separate bbt_xxx_quarto() function that adds the appropriate whitelists seems more explicit.

[dmi3kno]

whitelist_quarto=TRUE shifts the burden of maintenance on you as a maintainer of the package (same with bbt_xxx_quarto() plus duplication of code). Lots of things are specified in options(), including the width of dataframe print method (using pillar) and whatnot. I think options is a pretty standard solution. I am happy to remove it from .onLoad() and rely on user-specified options in the .Rprofile. Is that what you would prefer instead?

[mbojan]

No, please no option-setting by .onLoad()!