Enhance documentation for OCM setup action

[morri-son]

Description
The com-action should be retired and only the action to install the OCM CLI on a GH runner should be kept. Having the OCM CLI available should be sufficient to execute all possible actions with regards to OCM component versions.

There should be more documentation to guide end users:

• How to deal with configuration in the .ocmconfig file, store it as GH secret and get the config out of the secret to the place in the FS where it can be picked up from the CLI
• How to hand over a basic component-constructor.yaml for component version creation
• How to configure secrets for a target reg in the .ocmconfig file
• How to add a component version using a constructor file to a CTF archive
• How to transfer a component version using a CTF archive to a target registry