Update native APIs

[davidlehn]

When the native code is split out to another module (see digitalbazaar/rdf-canonize#5), also look at updating to N-API / node-addon-api. Should help with some portability issues.

https://medium.com/the-node-js-collection/native-extensions-for-node-js-767e221b3d26

[mattcollier]

Start here: https://github.com/digitalbazaar/rdf-canonize-native/tree/napi

It works, but there seemed to be a significant performance penalty vs current implementation. Hopefully it's just a matter of finding the offending code.

[davidlehn]

Yup, thanks for referencing that. I was just trying the "transfer issue" feature since this was still in the js project.