rs-promise

A simple promise implementation in rust

Usage

```rs

[tokio::test]

async fn test() {
    let promise = Promise::<String>::new();
    let mut promise_clone = promise.clone();
    let send_data = "111";
    tokio::spawn(async move {
        promise_clone.resolve(send_data.to_string()).await.unwrap();
        promise_clone.reject(send_data.to_string()).await.unwrap();
    });

    if let PromiseResult::Resolved(value) = promise.clone().await {
        assert_eq!(value, send_data);
    } else {
        panic!("error");
    }

    if let PromiseResult::Rejected(value) = promise.clone().await {
        assert_eq!(value, send_data);
    } else {
        panic!("error");
    }
}

```