Update init behavior

[jamesplease]

When using useReducer, init returns the state:

useReducer(reducer, initialState, () => {
  return {
    someState: true
  };
})

With the current API of this library, you must return the "internal" structure of the store:

useReducerWithSideEffects(reducer, initialState, () => {
  return {
    state: { someState: true },
    sideEffects: [] // you also must include this or else an uncaught exception will occur
  };
})

Users are unable to use Update/UpdateWithSideEffects/etc., because those don't return the correct key: they return newState rather than state.

I suggest refactoring Update/etc. to internally use the key state instead. That way, users of init can use a consistent API with this lib:

useReducerWithSideEffects(reducer, initialState, () => {
  return Update({ someState: true });
})

This change could even be released as a bug fix, I think, since it only changes non-public structures.

I'm curious to hear your thoughts on this @conorhastings !

[conorhastings]

haven't tested but esseentially something like this? #11

[jamesplease]

Resolved in 2.0.0-beta.2