[FR] allow relative URL to /media file in clickAction (of notifications)

On Android, is it possible to click through a notification, to display a media file located within the /media directory? This could already be supported, but I haven't been able to do so successfully.

With, for example:

```javascript
"image": "/media/local/amazon_order_2021-08-03_XXXX.jpg",
"clickAction": "/media/local/amazon_order_2021-08-03_XXXX.jpg"
```

The notification image displays fine, but a click leads to a 401: Unauth response (in the Companion app).