util: util.types.isProxy does not work in Node-ChakraCore

[jackhorton]

Causes test/parallel/test-util-types to fail.

[kfarnung]

Refs: chakra-core/ChakraCore#950

[jackhorton]

See 1e9ba64#diff-1980aca1cba9a1f0b7278ab1db2c064cR54

[rhuanjl]

Is there a reason not to support util.types.isProxy? The JsGetProxyProperties api I added to ChakraCore should enable supporting it. Unsure what the policy for contributing to node-chakracore - but I could try and make a PR to implement this if wanted?

[kfarnung]

No reason not to support it, we just hadn't gotten the chance to implement it yet. The contribution policy is the same as upstream node, feel free to open a PR.