Clean up ujson initialization
The way we do this now is a little wonky as we are declaring the C API in the objToJSON file for re-use by JSONToObj; this happens to work because we call the objToJSON initialization function in the main extension module, but it's a bit funky and prone to errors on refactor

More background info:

https://numpy.org/doc/stable/reference/c-api/array.html#importing-the-api

https://stackoverflow.com/a/35362918/621736