Add new Language in Core

Hi all,

I’d like to create a new Language which will be installed on install on any new instance. It’s the Swiss-German (de-CH).

Can anyone guide me through where to do this, that this is selectable in when running the install wizard of ERPNext.

I am aware, that we will need a copy of this:

and a new DocType of the Type Language

But I have no idea where to add this to the core and if this goes into frappe/frappe or frappe/erpnext

Thanks for your help!