Resonite supports multiple languages through the use of crowd-sourced translation files.
How to Use
By default, Resonite uses your system's language to determine which locale to use as default, and you will be asked to select your preferred one on 1st startup. You can change the language by going to Settings, User Interface, Locale, pressing Select Locale and choosing a different language.
Manually replacing locale files generally isn't needed as they are updated with the game, but can be helpful for testing updated translations before they are included in a new build. This tutorial covers how to manually update locale files.
Languages
How to Contribute
If you wish to contribute to the translation of a language, read over the readme on the Locale Github for information on the proper procedures.