Add Conda support

[Greedquest]

This fantastic extension just blows https://github.com/dpranke/pyjson5 out of the water in terms of performance (as in 3 orders of magnitude for loads), which probably makes sense given it is cython :)

However unlike that library, this is only installable via pip, not conda as well. Would you be able to add conda support?

[Kijewski]

I never used conda, and I don't know anything about it, sorry. But I'd be happy to accept your PR if you know how to add conda support. :)

[Greedquest]

I've know roughly the process. I know the first step is to create both a build dist and a source dist. This can be done by running python setup.py sdist. For example your repo contains https://pypi.org/project/pyjson5/#files only wheels whereas the other json5 library that is conda compatible contains https://pypi.org/project/json5/#files both wheels and source files in tar.gz format. It also recommends including the README in MANIFEST.in

If you are able to get a source dist up on pypi then I can look through the next steps and make a PR sure, but I can't do anything till then I don't think. Sorry, don't want to add to your workload.