Add combinators for repeating operations?

[cb372]

I was just looking at the docs for Bow: https://bow-swift.io/docs/effects/retrying-and-repeating-effects/

They support both retrying an operation until it succeeds (like cats-retry does), and repeating an operation until either it fails or the policy says we should stop.

I quite like this idea. We should be able to reuse RetryPolicy for repeating.

[Ssstlis]

I would like to work on it