Add Bark as a supported Apprise notification protocol.
Supported URL formats:
- bark://bark_key uses the official Bark server at https://api.day.app/
- bark://host/bark_key uses a custom Bark server over HTTP
- barks://host/bark_key uses a custom Bark server over HTTPS
Bark notifications are sent with POST JSON payloads containing the device key, title, and body. The notification settings modal now
lists Bark examples in the Apprise URL placeholder and support text.
