Webhooks - Virus risk event and Hub metadata added

🚀 Feature Release

• Virus risk feed is now released. Virus risk events are sent using a new type airthings-webhook-cloudevent-virus-risk-feed

• Hub metadata feed is now released. Hub events are sent using a new type hub-meta-data-feed and can be selected
  with the other devices/locations in the Dashboard.

About once every hour, the Hub sends metadata to the Airthings cloud informing us about its current status. A few example fields are connectionType (ethernet or cellular), lastSeenDevices(devices seen by the hub within the last 15 minutes), and devices, which shows all devices paired to the hub.

An example event:

{
  "id": "cb0bb746-cdb3-42b5-8a96-db88380e5513",
  "type": "airthings-webhook-cloudevent-hub-meta-data-feed",
  "source": "https://dashboard.airthings.com/integrations/webhooks/f278e95b-26e2-4942-8374-175611b98c36",
  "dataContentType": "application/json",
  "labels": {},
  "data": {
    "serialNumber": "2820000001",
    "recorded": "2020-11-13T13:46:08",
    "lastSeenDevices": [
      "2930000001"
    ],
    "devices": {
      "2930000001": {
        "lastSeen": 1598065353,
        "rssi": -57,
        "type": "wavePlus"
      }
    },
    "connectionType": "ethernet"
  },
  "time": "2020-11-13T13:46:10.280000",
  "specVersion": "0.2"
}

✨ Improvement

• Two new properties have been added to the data object: rssi (signal strength of the device) and batteryPercentage.