Choosing custom expire timeouts for any app

[ModalDiagram]

Before opening a PR I wanted to ask your opinion about a simple feature I added to the Notification manager.
I can now set a custom expire timeout for any app and also specify if the notification should be moved to the Notification panel or closed after expiration.

I found this useful for applications like Spotify that modify a notification fairly often.
At the current state the Spotify notification is hidden after expiration and following songs are not shown.
With this suggestion, Spotify would show the song title for a few seconds and then close the notification (so that it it will appear again at the start of the next song).

The configuration file would look like something like this:

    "notifs": {
        "actionOnClick": false,
        "clearThreshold": 0.3,
        "defaultExpireTimeout": 5000,
        "expandThreshold": 20,
        "expire": false,
        "appTimeouts": [
            {
                "appName": "Spotify",
                "expireTimeout": 3000,
                "closeOnExpire": true
            }
        ]
    },