Dynamic initial state based on machine's input

[JRebella]

Just like context can be created dynamically based on the machine's input:

Allow something similar for determining the initial state of the machine, for example:

initial: ({ input }) => {
    if (input.alreadyRegistered) {
      return 'login';
    }

    return 'register';
  },

Example use case:

In many scenarios you want to implement persistence to your flow but using the persistence feature of xstate doesn't apply. For example in a register -> login sort of flow, you'll want to check your database to see if your user exists and resume the flow at the login state, doesn't make sense to go around saving an xstate snapshot for cases like these

Workarounds

Currently this logic is able to be implemented manually but its truly a pain to do so, requiring you to create a dummy starting state and mapping out every possible transition from this starting state to any resumable state. Which also renders the flowchart of your machine unusable