Add Signal to ECS

- Add Signal class to ECS used to send signals/events into systems

CopiumEngine/src/copium/event/EventSignal.cpp

@@ -0,0 +1,15 @@
+#include "copium/event/EventSignal.h"
+
+namespace Copium
+{
+  EventSignal::EventSignal(const Event& event)
+    : event{event}
+  {}
+
+  const Event& EventSignal::GetEvent() const
+  {
+    return event;
+  }
+
+  CP_SIGNAL_DEFINITION(EventSignal);
+}