The Gutenberg plugin is translated via the general plugin translation system (GlotPress) at https://translate.wordpress.org. Review the GlotPress translation process documentation for additional information.
To translate Gutenberg in your locale or language, select your locale here and translate Development (which contains the plugin’s string) and/or Development Readme (please translate what you see in the Details tab of the plugin page).
A Global Translation Editor (GTE) or Project Translation Editor (PTE) with suitable rights will process your translations in due time.
Language packs are automatically generated once 95% of the plugin’s strings are translated and approved for a locale.
The inclusion of Gutenberg into WordPress core means that more than 51% of WordPress installations running a translated WordPress installation have Gutenberg’s translated strings compiled into the core language pack as well.