chore: add constructor func for ReplayObservable

pkg/observable/channel/replay.go

@@ -21,6 +21,15 @@ type replayObservable[V any] struct {
 	replayObservers   []observable.Observer[V]
 }
 
+// NewReplayObservable returns a new ReplayObservable with a replay buffer size
+// of n and the corresponding publish channel to notify it of new values.
+func NewReplayObservable[V any](
+	ctx context.Context, n int,
+) (observable.ReplayObservable[V], chan<- V) {
+	obsvbl, publishCh := NewObservable[V]()
+	return Replay[V](ctx, n, obsvbl), publishCh
+}
+
 // Replay returns an observable which replays the last n values published to the
 // source observable to new observers, before publishing new values.
 func Replay[V any](