Shoutrrr Notification support (incl. Pushover and many others)

[vorburger]

It would be cool if Keel supported sending its Notifications to https://pushover.net.

Pushover's API seems pretty straight forward.

Perhaps I will look into contributing this, some time.

PS: An alternative could be to just use Keel's Webhook integration, and hack a "bridge" from that to Pushover, outside of Keel.

[vorburger]

Instead of Pushover directly, probably to best is to integrate Shoutrrr (incl. Pushover, and others).