feat: time systems added

Engine.Systems/Time/IReadOnlyStopwatch.cs

@@ -0,0 +1,18 @@
+namespace Syntriax.Engine.Systems.Time;
+
+public interface IReadOnlyStopwatch
+{
+    event StopwatchEventHandler? OnStarted;
+    event StopwatchDeltaEventHandler? OnDelta;
+    event StopwatchEventHandler? OnStopped;
+
+    double Time { get; }
+
+    TimerState State { get; }
+
+    event StopwatchEventHandler? OnPaused;
+    event StopwatchEventHandler? OnResumed;
+
+    delegate void StopwatchEventHandler(IReadOnlyStopwatch sender);
+    delegate void StopwatchDeltaEventHandler(IReadOnlyStopwatch sender, double delta);
+}