Add option for digit to be allow number of significant digits like jsonlite::toJSON

[neovom]

Hi,

I really like the package and I saw that recently a digits option was added in this issue.

Is it possible to make the digits option take both K and I(K) arguments and when I(K) supplied we do "K number of significant digits", same as jsonlite::toJSON ?

Thanks!

[statquant]

I’m very interested in that feature as well