Support Healthchecks.io as an Alerting method

## Context
Healthchecks.io is a great platform for making sure that scheduled/recurring jobs are running. It would be relatively trivial to add support:

```
"Alerting": {
            "Healthchecks.io": {
                "URI": "https://yourhealtchecksio.url.here"
            }
}
```

And a simple `Invoke-RestMethod` call of the URI upon each run of the monitoring collection.