Implement URLSearchParams

[CGenie]

https://nodejs.org/api/url.html#class-urlsearchparams

We currently have Query as a very thin wrapper around nodejs querystring:

https://github.com/purescript-node/purescript-node-url/blob/v6.0.0/src/Node/URL.js#L2

Apparently this is legacy in the API:

https://nodejs.org/api/url.html#legacy-urlobject

It would be useful to implement URLSearchParams especially that I can't find anything for query manipulation on Pursuit. Query is bit tricky: there is URL escaping and whatnot. And it's often necessary when writing frontends that make requests for the backend.

[JordanMartinez]

Fixed in #20.