Hello I was wondering, if it is possible to add some Typescript types to make it a bit easier to work with this library in a typescript project (or even just for type hinting in an IDE)

I'm not looking for strong types for everything (but I mean why not :-D ) , but rather for some convenience helper types.
For example

const staticReducer = {
	foo: (state: 'foo', action) => state,
	nested: { bar: (state: 'bar', action) => state },
}

type State = StateFromDeepReducersMapObject<typeof staticReducer>

I already have a few of these and I'm willing to do a PR.
I'm also a bit afraid that once some types are added, all the exported members from the library have to be (to some extent) typed in order to be able to use them in TS project.
Sooo, I'm not saying I'm going to prepare a PR tomorrow but it could be soon enough. As long as I know somebody will have a look and possibly merge it 😉