add Moonpool_lwt.spawn_lwt_ignore

src/lwt/moonpool_lwt.ml

@@ -306,6 +306,8 @@ let spawn_lwt f : _ Lwt.t =
       with exn -> Lwt.wakeup_exn lwt_prom exn);
   lwt_fut
 
+let spawn_lwt_ignore f = ignore (spawn_lwt f : unit Lwt.t)
+
 let lwt_main (f : _ -> 'a) : 'a =
   let st = setup () in
   (* make sure to cleanup *)

src/lwt/moonpool_lwt.mli

@@ -27,6 +27,9 @@ val spawn_lwt : (unit -> 'a) -> 'a Lwt.t
 (** This spawns a task that runs in the Lwt scheduler.
     @raise Failure if {!lwt_main} was not called. *)
 
+val spawn_lwt_ignore : (unit -> unit) -> unit
+(** Like {!spawn_lwt} but ignores the result, like [Lwt.async]. *)
+
 val await_lwt : 'a Lwt.t -> 'a
 (** [await_lwt fut] awaits a Lwt future from inside a task running on a moonpool
     runner. This must be run from within a Moonpool runner so that the await-ing