Allow CarbonImmutable for CarbonPayload

[abenerd]

In my Laravel projects I prefer CarbonImmutable over Carbon, therefore I propose that when instantiating the \Spatie\Ray\Payloads\CarbonPayload to allow an instance of CarbonInterface to be the argument rather than the more specific Carbon class. This would allow people to use both Carbon and CarbonImmutable.

[freekmurze]

Good idea, please send a PR for this.

If no PR comes in, I'll take care of it soon.

[freekmurze]

Thanks for the PR, merged!

[abenerd]

Great, thanks!