This Magento 2 module adds the ability to add an extra language file to your theme.
Every theme has the ability to override language strings in a file like
i18n/en_US.csv. This module allows you to add a second file
i18n/en_US_additional.csv which is loaded on top of the original file.
The benefit of this is that you can have a parent theme that fills up
en_US.csv which is then inherited in the child theme. Yet using
this module, you can make specific overrides in the additional language
Install this module within Magento 2 using composer:
composer require yireo/magento2-additional-language-file
And of course afterwards use the regular commands to enable the module.
This module remaps the preference for the original
Magento\Framework\Translate file to a new class.