Investigate adding a proxy-based selector API

Both our connect and useSelector APIs rely on the user manually specifying what pieces of state to extract to determine re-renders.

@dai-shi has done some amazing work with using ES6 Proxies to manage tracking the pieces of state that are actually needed by a component, particularly in his https://github.com/dai-shi/reactive-react-redux library.

I’ve said several times that I kinda see that lib as a sort of alpha test for whether an approach like that should be added to React-Redux itself. Now that our hooks API has been stable for a while, it might be time to start discussing that idea more seriously.

This may also have some relevance to the Concurrent Mode questions over in #1351 .

Ideally, anything we add would be completely tree-shakeable by default, so that it doesn’t increase bundle size unless the API is actually used.

[timdorr]

FWIW, we decided against the useReduxState name early on in the planning process for hooks.

[theKashey]

Ideally useTrackedState should also report an “illegal” uses, when to many entities are being tracked. Personally, for the last year, I am using tracked selectors mostly to “prove” than my manual selectors are working correctly, and will continue doing it correctly and performant(!) without tracking as well.