Provided by CategoriesProvider to useCategories, for the category
switchers and pickers, the dump and playlist pages and cards, and the
category manager.
Every category, dump and playlist ones, in the server's order, by kind, position then slug.
isLoaded: boolean
Whether the first fetch has ended. It is also true after a network error, with no categories.
refresh: () => Promise<void>
Refetches the list. The category manager calls it after each change.