Would it be possible to add the deep_merge options?

[geoffr]

I would like to extended the deep_merge method deeper with more options, for example:

:merge_behavior: deeper
:deep_merge_options:
  :extend_existing_arrays: true
  :merge_hash_arrays: true

[geoffr]

Faking it for now with

hiera_merge_behavior => 'deeper
:deep_merge_options:
  :extend_existing_arrays: true
  :merge_hash_arrays: true',

[rendhalver]

That should be pretty easy to setup.
I am happy to accept a PR if you have the time to write up the code.
I am generally pretty busy these days and it might take me some time to get to it.