CV: add CLI option that prevents users from using tags that are not part of the used .filetags file

[novoid]

I want to force the user(s) to use only pre-defined tags that are part of the controlled vocabulary. Please add a CLI option like --force-cv (or: --prevent-unknown-tags or ?).

FIXXME: find the most appropriate option name

[novoid]

https://github.com/beutelma/filetags.el provides this as well.

[novoid]

This would be only a convenience feature since modifying file names outside of filetags is - of course - always an option. The proposed feature would prevent typos within the interactive or non-interactive adding functions.