* Move useSyncExternalStore shim to a nested entrypoint
Also renames `useSyncExternalStoreExtra` to
`useSyncExternalStoreWithSelector`.
- 'use-sync-external-store/shim' -> A shim for `useSyncExternalStore`
that works in React 16 and 17 (any release that supports hooks). The
module will first check if the built-in React API exists, before
falling back to the shim.
- 'use-sync-external-store/with-selector' -> An extended version of
`useSyncExternalStore` that also supports `selector` and `isEqual`
options. It does _not_ shim `use-sync-external-store`; it composes the
built-in React API. **Use this if you only support 18+.**
- 'use-sync-external-store/shim/with-selector' -> Same API, but it
composes `use-sync-external-store/shim` instead. **Use this for
compatibility with 16 and 17.**
- 'use-sync-external-store' -> Re-exports React's built-in API. Not
meant to be used. It will warn and direct users to either the shim or
the built-in API.
* Upgrade useSyncExternalStore to alpha channel
6bce0355c3