tz: Time Zone CLI app using CUE as its config language

[DavidGamba]

Embedding cue schemas and using them in CLI tools to unmarshal config is super easy with CUE.
Additionally, users can create reusable _temporary variables that make their configs more concise.

This simple CLI app demonstrates those features and some might find it useful:

https://github.com/DavidGamba/dgtools/blob/master/tz/README.adoc

The schema definition is here:
https://github.com/DavidGamba/dgtools/blob/793ec59816c009127a8011aad189a7562e537916/tz/schema.cue

And it gets embedded and unmarshalled here:
https://github.com/DavidGamba/dgtools/blob/793ec59816c009127a8011aad189a7562e537916/tz/config.go