Incorrect typings for GroupByFunction

[gaopinghuang0]

The typings for GroupByFunction are as below.

  type GroupByActionTypes = (actions: string | string[]) => GroupByFunction;
  export type GroupByFunction = <State>(action: Action, currentState: State, previousHistory: StateWithHistory<State>) => any;

However, GroupByActionTypes is actually returning an arrow function accepting only one action.

export function groupByActionTypes (rawActions) {
  const actions = parseActions(rawActions)
  return (action) => actions.indexOf(action.type) >= 0 ? action.type : null
}

So I think the typing would be something like below.

  export type GroupByFunction = (action: Action) => any;

[louisrli]

+1: I'm also finding some misc typing issues here

[nmay231]

Resolved in #248 👍