Add simple examples for MS queue

examples/dune

@@ -0,0 +1,3 @@
+(executables
+ (names michael_scott_queue)
+ (libraries lockfree))

examples/michael_scott_queue.ml

@@ -0,0 +1,20 @@
+open Lockfree.Michael_scott_queue
+
+let push_work_pop queue item =
+    push queue item;
+    for _ = 1 to 100_000_000 do 
+        (* do other work *)
+        ignore ()
+    done;
+    match pop queue with
+    | Some v -> Printf.printf "pushed %d and popped %d\n" item v
+    | None -> failwith "pop failed: empty list"
+
+let main () =
+    let ms_q = create () in
+    let d1 = Domain.spawn(fun _ -> push_work_pop ms_q 1) in
+    let d2 = Domain.spawn(fun _ -> push_work_pop ms_q 2) in
+    let d3 = Domain.spawn(fun _ -> push_work_pop ms_q 3) in
+    Domain.join d1; Domain.join d2; Domain.join d3
+
+let _ = main ()