Add StateFactory

[Knoxvillekm]

Add function to create MutableValue of state and save it to stateKeeper.

inline fun <reified S : Parcelable> ComponentContext.state(
    initialState: S,
    key: String = "DefaultState"
): MutableValue<S> {
    val state: S = stateKeeper.consume(key = key) ?: initialState
    val value = MutableValue(state)
    stateKeeper.register(key = key) { value.value }
    return value
}