Update user guide to include public docker image information

[andygrove]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
In various places in the user guide, we currently state that "There are no officially published Docker images, so it is currently necessary to build the images from source.". This is no longer true.

Describe the solution you'd like
Reference the public docker image instead.

Describe alternatives you've considered
None

Additional context
None