feature request: option for useStore.subscribe fire once on initialisation

Currently useStore.subscribe only fires when the subscribed part of the store changes. It would be useful if there was an option to force the function to fire once upon initialisation. Maybe I’m missing something, here’s an example:

useEffect(() => {
    // I don't want to have to repeat myself up here just for initialisation
    const { position, rotation } = getSceneObject(props.id)(useStore.getState())
    target.current.position.set(position[0], position[1] - 3, position[2])
    plane.current.position.set(...position)
    plane.current.rotation.set(rotation[0], Math.PI, 0)

    return useStore.subscribe(
      ({ position, rotation }: SceneObject) => {
        target.current.position.set(position[0], position[1] - 3, position[2])
        plane.current.position.set(...position)
        plane.current.rotation.set(rotation[0], Math.PI, 0)
      },
      (state) => getSceneObject(props.id)(state)
    )
  }, [props.id])

[timothyallan]

Just dropping in my 2c here to think about for potential future dev: I use this feature all the time in MobX. They have optional params you can pass into the subscribe function, one is called fireImmediately, which does exactly what it sounds like.

[dai-shi]

I will try this feature (fireImmediately option) along with #555. It will be a new middleware.