Hello.
First of all thank you for the library, it works really great!

I've just bumped into one issue. In our setup we have iframe & parent window running on same domain and interacting with one another.

One of those interactions is:

const intialState = iframe.someFunction();

const state = create(initialState, ...);

Due to this, even though the returned object is "simple", the Object.getPrototypeOf(value) === Object.prototype check fails.

I can overcome this by using mark functionality:

const state = create(initialState, ..., {  mark: () => "immutable" });

This brings a couple of questions:

1. Is it okay to simply use mark: () => "immutable",? Will this lead to some side effects? I haven't digged too deep into the source code yet, but couldn't find info in the docs.
2. Next to mark docs, it says that (AutoFreeze and Patches should both be disabled). Is that really the case? I've tried to use them with mark and it looked like it works fine.
3. Maybe there is a different kind of "simple" object check that would not break in this crazy scenario?