Inform about unused language keys

[Zerotask]

Is your feature request related to a problem? Please describe.
It would be nice to inform the devs about unused language keys.

Describe the solution you'd like
A simple console output

How important is this feature to you?
Not important

[brunnerh]

You would need a build tool plugin that analyzes the entire code base and even then, as soon as you start building keys from parts (e.g. using a common prefix), sometimes even split into separate functions, it becomes near impossible. Your dictionaries have to be statically analyzable as well, which is not always the case.