Map.prototype.values() method not implemented

[croraf]

ECMASCript feature
https://www.ecma-international.org/ecma-262/11.0/index.html#sec-map.prototype.values

Example code

const map1 = new Map();

map1.set('0', 'foo');
map1.set(1, 'bar');

const iterator1 = map1.values();

console.log(iterator1.next().value);
// expected output: "foo"

console.log(iterator1.next().value);
// expected output: "bar"

[JohnDoneth]

I have that exact code working in a test on a branch. Implementation needs more work though. I will submit a PR when it's ready for review.

Looks like #847 should address this once finished by changing the iterator Kind to Value.