feat: add optional post-install-notes to each registry item.

[MihalyToth20]

The registry implementation currently uses xanoscript, and as a result we have no option of setting up environment variables. And this is good as it is, we don't want to tamper with envvars.

But obviously some components will always require manual configuration, adding secrets, or simply adjusting the defaults.

We have to give two options to the users:

1. set up the required values at the installation step, via either CLI prompting (more complex due to lack of schema definition support yet in the registry) or via a config file which would open up, but this could break the AI-capabilities of the CLI.
2. First step maybe just to instruct the developer to update the required values. This post-install note should be stored at the registry item level, and be presented in the CLI following successful installation. Obviously the registry items have to have these comments inline as well in the xanoscript that is being uploaded just to keep it in sync everywhere.