[Suggestion] Add webhook support to update a Library

I’ve been always curious about finding a better way to update specific libraries, it would be nice if a Webhook was available so I can tie it in with smart home devices.

A webhook is going out from your plex server. i.e. you won’t be able to use them for sending commands towards the server.

see https://support.plex.tv/articles/201638786-plex-media-server-url-commands/

Early 2021 clean-up: implemented