reducer factory without state

[goblindegook]

Expose a factory function for reducers that does not require passing the initial state:

function reducer<S>(): EnhancedReducer<S>

This would allow for a more concise use with the useReducer React hook, which provides the initial state separately, so instead of...

const example = reducerFromState(INITIAL_STATE)
  .on(action, state => state)

const [state, dispatch] = useReducer(example, INITIAL_STATE)

...we'd have...

const example = reducer<typeof INITIAL_STATE>()
  .on(action, state => state)

const [state, dispatch] = useReducer(example, INITIAL_STATE)