[Nix-dev] Adding documentation to nixpkgs

[Michel Kuhlmann]

Hi,
I just wanted to update the R-CRAN-packages and I always forget how to
check if the resulting expression could be evaluated.

Therefor I created a basic README.md [1] directly within nixpkgs.

So is this desirable or do you think this clutters up the source-tree?

Greetings, Michel

P.S.: For me, the wiki is not really accessible (I like to work
offline in the train) and despite of that I don't like to write
in mediawiki markup.

[1]: https://raw.githubusercontent.com/michelk/nixpkgs/r-modules/update/pkgs/development/r-modules/README.md