Feature request for onError and retry

[georgiosd]

Hi!

We'd love two features that we're willing to send PRs for:

1. Support promises on the retry func - we want to be able to ask the user if s/he wants to retry

2. Ability to fallback to the global onError handler from the local handler. Either by passing an extra argument to onError, or exporting a useReactQueryConfigContext so we can manually get the onError handler

Whatcha think?