auto proxySet/proxyMap in proxy, and auto new Set/ new Map in snapshot

[magicdawn]

background, when persist data is needed, serialization / deserialization is need.
the superjson supports Map/Set serialization / deserialization

when use set/map with valtio, things need to be done

1. load storage -> superjson.parse(may contains Map/Set) -> transform map/set to proxySet/proxyMap -> valtio.proxy(transformed)
2. when state change -> valtio.snapshot(state) -> transform snapshot-of-proxySet/proxyMap to real Set/Map -> superjson.stringify -> save to storage

AS u can see, it would be nice for proxy() support real Set/Map: auto transform to proxySet/proxyMap

[dai-shi]

Thanks for opening up the discussion.

Valtio's design decision is that it doesn't support native Set/Map. So, proxySet/Map is implemented as an emulation.
Now, your suggestion sounds reasonable. Currently, customizing set trap of a Valtio proxy isn't supported. And, only the solution is a low-level function unstable_buildProxyFunction.
#909 (comment)

We would like to collect more feedback on the low-level function and re-design a new/better/extensible API for the future version of Valtio.

[dai-shi]

Auto proxySet/Map might be technically possible with new internals exposed.

Also, I opened up a new discussion: #943