Add `MessageEvent`/`MessagePort`

[JordanMartinez]

Prerequisites

• Before opening an issue, please check the HTML standard (https://html.spec.whatwg.org). If it doesn't appear in this spec, it may be present in the spec for one of the other purescript-web projects. Although MDN is a great resource, it is not a suitable reference for this project.

Description

See purescript-web/purescript-web-workers#6. I think MessageEvent and MessagePort should be added here so it can be used in web-workers.