[#237] Allow filtering state properties before save it to history

[GeorgeGkas]

No description provided.

[munen]

This would be great to have.

I'm using redux-undo in https://github.com/200ok-ch/organice and was thinking of how to do what you did.

Is there something I can do to help with the approval / merge process?

[Goues]

Just a note from another user of redux-undo: In this case, it would make sense to just compose this as two reducers and then wrap only one of them with undoable.

Something like:

const baseReducer = combineReducers({
  position: positionReducer,
  count: undoable(countReducer),
})

I understand this is a very simplistic example, but I think it can be extrapolated to any scenario - you can simply put the data you want to be ignored into another slice of state and call it a day. What would be the benefit of filtering like this?