Add support for ntfy

[cpatscheider]

Current State:

Notifications to ntfy can be triggered via the generic webhook notification.
However this results in receiving the json as plain text notification:

Target State:

Native ntfy support shall be added via seperate environment variables for configuration.
E.g.:
NTFY_ENDPOINT
This will allow to post the notification in a way to output nice ntfy notifications:

Optional

• Mapping of log level to ntfy priorties. E.g.: ERROR -> MAX_PRIORITY
• Support for Authentication (ntfy is open by default)

Implementation

Should be very similar to the Discord implementation using the go implementation snippet from the ntfy website: https://docs.ntfy.sh/publish/#tags-emojis

[cpatscheider]

I am gonna try myself out on this one, since it looks pretty straight forward.
Bear with me since this is my first contribution .