There isn’t anything specific for localization yet. You can save a value in Session State to set a version and then conditionally fill in your app with the correct language based on the value in Session State.
Streamlit does offer some ability to read the user’s context if you want to try and determine in advance what language should be set, but ultimately you’ll have to store and read from a saved value to determine what language to use, and conditionally pull those language strings yourself in situ.