add a getProviders composable to useAuth

[BayBreezy]

I was just testing out the module and realized that it does not have a getProviders composable.

I was in the process of implementing a custom sign in page when I realized this. So on the sign in page, I added this code

const { data, pending, error, refresh } = await useAsyncData("auth-providers", () =>
  $fetch("/api/auth/providers")
);

Not a big deal, just a nice to have

[Hebilicious]

That could be a great addition. PR welcome !

[Hebilicious]

Implemented