An enum similar to Poll, but containing a future in its Pending variant

Example

```rust use futureslite::future; use futurespolling::{FuturePollingExt, Polling};

let mut polling = async { future::yield_now().await; 42 }.polling();

asserteq!(polling.ispending(), true);

// Poll just once. polling.pollingonce().await; asserteq!(polling.is_pending(), true);

// Poll until the inner future is ready. assert_eq!(polling.await, 42); ```

License

This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.