Developer flow for publishing from CI should be more intuitive

* [x] I have read the [contribution documentation](https://github.com/electron-userland/electron-forge/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [code of conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project follows, as appropriate.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

Is it possible to publish artifacts without having to rebuild everything? I'm trying to just take all the artifacts as built on CI and shove them up the Microsoft GitHub release.

Still using **version 5**

**What command line arguments are you passing?**

```
electron-forge publish --auth-token {theToken}
```

Naturally, when I run the command, it fails on me because it is already running on a different "machine", one that does not have capabilities to build packages.

This is how the build flow looks like:

**What does your `config.forge` data in `package.json` look like?**

```
"config": {
"forge": {
"make_targets": {
"win32": [
"squirrel"
],
"darwin": [
"zip"
],
"linux": [
"deb",
"rpm"
]
},
"electronPackagerConfig": {
"packageManager": "npm",
"asar": true
},
"electronWinstallerConfig": {
"name": "radio_drama_soundboard"
},
"electronInstallerDebian": {},
"electronInstallerRedhat": {},
"github_repository": {
"owner": "just-paja",
"name": "radio-drama-soundboard"
},
"windowsStoreConfig": {
"packageName": "",
"name": "radiodramasoundboard"
}
}
}
```