InvokeAI uses Weblate for translation. Weblate is a FOSS project providing a scalable translation service. Weblate automates the tedious parts of managing translation of a growing project, and the service is generously provided at no cost to FOSS projects like InvokeAI.
If you'd like to contribute by adding or updating a translation, please visit our Weblate project. You'll need to sign in with your GitHub account (a number of other accounts are supported, including Google).
Once signed in, select a language and then the Web UI component. From here you can Browse and Translate strings from English to your chosen language. Zen mode offers a simpler translation experience.
Your changes will be attributed to you in the automated PR process; you don't need to do anything else.
Please check Weblate's documentation or ping @psychedelicious or @blessedcoolant on Discord if you have any questions.
Thanks to the InvokeAI community for their efforts to translate the project!