Rich Colors on individual toast basis

[nicksrandall]

Describe the feature / bug 📝:

I'd like to opt into the "richColors" styles on a per-toast basis. It would be great if I could pass that option to the toast function so that that specific toast is opted into rich colors styles. I'd be happy to make a PR if you're open to this change.

[nicksrandall]

I believe this is a non-breaking change as we still follow the richColors value set on the <Toaster /> if not passed directly to the individual toast.

[emilkowalski]

Merged your PR!