Add URL

[kitsonk]

Fixes part of: #1047

This PR adds the URL global object which makes it easier to parse URL and work with their parts. The code tries to functionally replicate the Web Standard but doesn't follow the logic of the standard (which has a lot of obtuse and obscure logic in the IDL).

[LinusU]

What do you think about adding the following test, which passes in Safari 12.0.2 and Node.js 11.1.0, but which I think will fail here since the value of hash is encodeURIComponent-ed on the way in, but not decoded on the way out.

test(function urlBaseString() {
  const url = new URL("http:https://example.com");
  url.hash = "%test";
  assertEqual(url.hash, "#%test");
  url.hash = url.hash;
  assertEqual(url.hash, "#%test");
});

[ry]

A clean new URL implementation - awesome! Looks good - but please add the test @LinusU suggests.

[ry]

Do other URL implementations use RegExp?

[kitsonk]

Node.js uses a combination of splitting strings and regular expressions. It's url is a slightly different beast to the the whatwg URL. JSDom follows the IDL pedantically, so it ingests each character and does loads of branching. While it complies 100% including the logic, it is a lot of code. There are two other polyfills that I found on npm, one ingests per char, the other uses regular expressions.

[kitsonk]

@LinusU thanks for the heads up. I also found a couple issues with the .pathname setter as well.

[ry]

LGTM