Improve AsyncResult doc

Author: Fedeparma74

lightning/src/util/async_poll.rs

@@ -93,10 +93,10 @@ pub(crate) fn dummy_waker() -> Waker {
 }
 
 #[cfg(feature = "std")]
-/// A type alias for a future that returns a result of type T.
+/// A type alias for a future that returns a result of type `T` or error `E`.
 pub type AsyncResult<'a, T, E> = Pin<Box<dyn Future<Output = Result<T, E>> + 'a + Send>>;
 #[cfg(not(feature = "std"))]
-/// A type alias for a future that returns a result of type T.
+/// A type alias for a future that returns a result of type `T` or error `E`.
 pub type AsyncResult<'a, T, E> = Pin<Box<dyn Future<Output = Result<T, E>> + 'a>>;
 
 /// Marker trait to optionally implement `Sync` under std.