(middlware/persist): Limitations are not documented

[C-Otto]

Based on #618 and #652 there are limitations to what can be stored. Aside from the actual reasons for this limitation, users should be made aware of this. If this can be done using the typesystem for TypeScript users, that'd be great (I'm used to Java). If not, please add a big fat warning so that users don't run into issues. Without proper documentation, there's no way to know if the code you're going to write is going to work. Trial-and-error isn't a viably alternative for me, YMMV.

From #618:

By default, persist serializes the state using JSON.stringify.
Unfortunately JSON doesn't fit very well with Sets and Maps.

To me that sounds like a bug, not a documentation issue. If JSON doesn't do what you need it to do, don't use JSON (or fix it).

[dai-shi]

With #1463, we will be able to customize storage to support Maps and Sets.

If anyone has ideas for more improvements, please feel free to open PRs.

[C-Otto]

Until #1463 is done, please document this behaviour so that users are not surprised. To me, using sets and maps isn't any different from using other data structures (and primitives). This doesn't match zustand's expectation/offering, causing frustration.

[dai-shi]

If you have suggestion how to document it, can you please open a PR? The doc is at: https://github.com/pmndrs/zustand/blob/main/docs/integrations/persisting-store-data.md

If you are interested in using maps and sets, please help us by trying #1463 and suggesting how to document it.

[C-Otto]

I stopped using JS/TS for my projects. Others might be interested in this, though.