feat(callback): add callback utils (#18)

plugin/src/util/Callbacks.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Linq;
+using UnityEngine;
+
+namespace PiUtils.Util;
+
+public class Callbacks
+{
+	public static Action<T> Debounce<T>(Action<T> callback, float seconds)
+	{
+		Coroutine timeout = null;
+		T lastValue;
+
+		return (T arg) =>
+		{
+			lastValue = arg;
+			if (timeout != null)
+			{
+				return;
+			}
+
+			timeout = AsyncGameObject.Timeout(() =>
+			{
+				timeout = null;
+				callback(lastValue);
+			}, seconds);
+		};
+	}
+
+	public static Action<T> Unique<T>(Action<T> callback)
+	{
+		Option<T> lastValue = Option<T>.None();
+
+		return (T arg) =>
+		{
+			if (lastValue.Contains(arg))
+			{
+				return;
+			}
+
+			lastValue = Option<T>.Some(arg);
+			callback(arg);
+		};
+	}
+}