Beta release channel

[somebeaver]

From now on I'm going to be publishing the work-in-progress to a new beta release on Docker Hub, which will receive more frequent updates than the stable release. I've also created a new beta forum for feedback on stuff in progress.

More info on release channels here: https://help.cardinalapps.io/guides/cardinal-home-server/release-channels

Beta release: https://hub.docker.com/r/cardinalapps/home-server/tags

[douglasparker]

Awesome, this sounds great!