Doesn't work on Node 12 — PRs submitted for dependencies

Nobody has claimed this yet.

Appdmg currently doesn't work on Node 12, because compilation of native code in two dependencies was broken by a change in the V8 API.

The dependencies in question are [macos-alias](https://github.com/LinusU/node-alias) (via [ds-store](https://github.com/LinusU/node-ds-store)) and [capture-window](https://github.com/LinusU/node-capture-window), all of which you own. I have submitted PRs LinusU/node-capture-window#2 and LinusU/node-alias#16 to fix this problem by converting them to use N-API, which unlike the V8 API is guaranteed to remain stable. When I manually applied them to my local copy of appdmg, it built successfully and all tests passed on Node 12.

---

In the mean time, in case anyone else needs it, my fork of appdmg has [a branch “node-12-temporary-fix”](https://github.com/argv-minus-one/node-appdmg/tree/node-12-temporary-fix), which brings in the patches to macos-alias and capture-window. To use it, in `package.json`, set the version of your appdmg dependency to `argv-minus-one/node-appdmg#node-12-temporary-fix`. Example:

```json
{
"dependencies": {
"appdmg": "argv-minus-one/node-appdmg#node-12-temporary-fix"
}
}
```

Start with package.json and the dependency PRs for node-capture-window and node-alias, then check how appdmg brings in ds-store and macos-alias. Confirm the upstream N-API fixes are available, update the dependency references as needed, and verify that appdmg builds and its tests pass on Node 12.

Written by the indexing model from the issue text.