Make mocked registry more visible

[renejeglinsky]

I think this is an important part that could be missed easily. I gave it a try to include it early on.

[chgeo]

As discussed, we should only mention the registry in a 'Deployment/Publishing' section, but not make users install modules from beginning on.

[danjoa]

Yes, maybe we need to clarify its usage:

• during development / experiments you should work with monorepo setup → node_modules in root only
• local installs are required for deployment only, or for simulating isolated development

Important is: never mix both!

[renejeglinsky]

I made changes that hopefully match your suggestions. Pls give it a review. Thanks.