Add more documentation

knots/queue.scm

@@ -25,6 +25,12 @@
   #:export (spawn-queueing-fiber))
 
 (define (spawn-queueing-fiber dest-channel)
+  "Spawn a fiber that serialises items onto DEST-CHANNEL in FIFO order.
+Returns a new input channel.
+
+Multiple producers can put items on the returned channel concurrently.
+The fiber buffers them locally and forwards them to DEST-CHANNEL one at
+a time, preserving arrival order."
   (define queue (make-q))
 
   (let ((queue-channel (make-channel)))