Simple promise library compatible with std::future and async/await
Create a promise and wait for the result while computing the result in another thread
```rust use pinky_swear::{Pinky, PinkySwear}; use std::{thread, time::Duration};
fn compute(pinky: Pinky fn main() {
let (promise, pinky) = PinkySwear::new();
thread::spawn(move || {
compute(pinky);
});
assert_eq!(promise.wait(), Ok(42));
}
```