Make using allowAllTransitions() less cumbersome

[jonjakoblich]

One of the great things about this package is that it will automatically load states that are placed in the same directory as the abstract base state class. There is no need to manually register concrete states in the same directory...with one exception - the allowAllTransitions() config method.

Currently the docs show the following example:

abstract class PaymentState extends State
{
    // …

    public static function config(): StateConfig
    {
        return parent::config()
            ->allowAllTransitions();
    }
}

However, this code is not possible to execute without it throwing a Spatie\ModelStates\Exceptions\InvalidConfig exception.

My pull request updates the allowAllTransitions() method to automatically register the concrete state classes in the same directory as the abstract base state class, thereby making the above code work as a user might expect.

This eliminates the cumbersome overhead of explicitly registering every state in the same directory when using allowAlltransitions().

[freekmurze]

Thank you!