Add a lock option

### Please agree to the following

- [x] I have searched [existing issues](https://github.com/cryptomator/cli/issues?q=) for duplicates
- [x] I agree to follow this project's [Code of Conduct](https://github.com/cryptomator/cli/blob/develop/.github/CODE_OF_CONDUCT.md)

### Summary

CLI should display a mean to lock the vault

### Motivation

New to Cryptomator and happy to see there is an official CLI.
But CLI help is a bit terse. It would be nice to display how to unmount the drive and close/lock the vault. I haven't tried on Linux/Mac, but on Windows, there remains a zombie mounted drive. A clean way to lock should be displayed in my opinion :-).

### Considered Alternatives

_No response_

### Anything else?

_No response_