Update documentation to include --vault usage with micado up CLI

[kotak-Gunjan]

Currently, the documentation does not explain how to use the --vault flag when deploying MiCADO via the CLI using micado up.

Request:
Please update the documentation to include:

A brief explanation of what the --vault flag does.

When and why a user would use --vault (e.g., for injecting secrets securely).

Any required preconditions (e.g., Vault must already be set up and running).

A CLI example showing how to run the deployment with the --vault flag.