Deprecate this library in favor of `shipengine-ts`

[kyle-villeneuve]

This repo is pretty much dead and very outdated compared to what the ShipEngine API currently supports. After putting up with it for a couple of years I ended up writing my own with much better type safety coming directly from the https://github.com/ShipEngine/shipengine-openapi spec. The one major drawback is that it currently does not support camelCase, other than that, in my biased opinion (as the author) it's superior in basically every way, and should be virtually painless to upgrade as the ShipEngine API evolves.

pkg: https://www.npmjs.com/package/shipengine-ts

code: https://github.com/kyle-villeneuve/shipengine-ts

[kyle-villeneuve]

@AnneOReilly