[Nix-dev] pyenchant: new package

[Nick Sauce]

I'm fine with trying to keep things working, but I don't have a GitHub 
account and would prefer not to use them.

FWIW, GitHub's terms of service might forbid a bot that would open PRs:

  https://help.github.com/articles/github-terms-of-service

Thanks for the consideration though (and thanks Vladimir for the reviewing
and committing of earlier patches).