ui: documentation tweaks

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/input/input.go

@@ -33,6 +33,8 @@ package input
 // Queue maps an event handler key to the events
 // available to the handler.
 type Queue interface {
+	// Next returns the next available event, or
+	// false if none are available.
 	Next(k Key) (Event, bool)
 }