Implement a new `useStoreProxy` hook that provides access to read and
update the store in UI components. This will replace the existing
`useStore` hook.

The new hook has a more ergonomic API which should also prevent some of the
common mistakes made when using the previous hook.

`useStoreProxy` returns an ES proxy for the store. The UI component can
use the proxy as if it were using the store directly. The proxy however
tracks and caches the results of store selector calls. When the store
state changes the proxy checks whether any of the cached calls would
return different results and if so invalidates the cache and re-renders
the component.