Summary:
I think a common pattern is to use async functions with the onRefresh prop to reload data. I made the type `mixed` since we don't care about what the function returns. Could also be `void | Promise<void>` I haven't really seen a pattern for those in the codebase.
Pull Request resolved: https://github.com/facebook/react-native/pull/22376
Differential Revision: D13310372
Pulled By: TheSavior
fbshipit-source-id: 445f28cf2c37f9c937e72d76716002deaf9d9c94