1. Fetch available languages. (page summary endpoint? JS bridge?) [DONE]
2. Add language picker to the toolbar. Enable if there are other languages available. [DONE but always enabled]
3. Ensure available language count also shows in article footer. [DONE]
4. Present the available languages and push on another article view in the correct language once selected. [DONE]
5. Ensure available languages logic works in offline mode. This might mean caching whatever response contains available languages. (or hide it, or show an error when they tap on it) [DONE]
6. (Maybe break this off into another task) To handle language variants, we would need to store it in a separate article key and either give the user the option to switch or switch for them based on device settings. The accept-language header is what causes it to vary, so if you lookup with a URLRequest, it can reference the header to see if it matters and if so, add the variant to the key for lookup. `Accept-Language, Accept-Encoding` [DONE, but needs more testing]