Improve Docs to include example of actual docker startup

[jamesnyika]

What is currently missing?

The documentation does not mention the entry point information for docker containers

How could this be improved?

Please add an example showing the actual command to start karapace. the Entrypoint information is not documented anywhere and only through an example did I locate it.. :

/bin/bash /opt/karapace/start.sh registry
and
/bin/bash /opt/karapace/start.sh rest

Is this a feature you would work on yourself?

Nope.

[ ] I plan to open a pull request for this feature

[kanapuli]

Also, it would be better to have documentation on how to run/start the Karapace application without a docker setup. Will be super helpful for feature development and debugging.