Adding / Removing languages

I’n interested how to add new language translation to Spark and how to remove some not nessesary ones.

Yet I have successfully modified spark_i18n8 files and make my language available under different languages

But I want to create my spark_i18n.properties file and add my language support to spark.

Creating Only custom spark_i18n.properties file to resource does not make language vailable in menu,

As I gues I should add lang file in one of build or properties files.