Separate H3 dependency and move to Suggests

[JosiahParry]

Building H3 requires a C compiler. Installing H3 is tough for non-mac users. No h3 bindings are published to CRAN which is problematic.

Once I identify, or create, an H3 library, it will need to be moved to Suggests.

[Joe-Wasserman]

This would be a great addition, as a Windows user at a Windows shop. One easier(?) option might be to split the package into two:

1. The first package containing all of the core placekey functions that doesn't require h3/Rcpp.
2. The second package requiring the placekey package and containing all of the h3-required functions.

[JosiahParry]

I'd agree. I unfortunately do not have the requisite knowledge of C & Make to do this effectively on my own.

[sovitchalise]

Thanks for your work on this.

I am trying to install h3 on windows to use the placekey API on R. I read your comments on this issue. There is a h3 binding for R I recently came across called "h3-r" (source: https://github.com/crazycapivara/h3-r). However, the binding doesn't directly work with the placekey package in R. The h3-r installs fine but installing placekey throws an h3 error. I think maybe the "h3-r" package can be used in placekey instead of h3. What do you think? This may resolve the issue for windows users and dependency on a non-R package altogether?

[JosiahParry]

Hey folks! Tagging @aseemdeodhar for visibility.

@sovitchalise, do you know if the h3-r bindings are robust and compile effectively on windows?