Allow [System]s and [Observer]s can be non-public

src/gaemstone/ECS/Universe+Modules.cs

@@ -211,7 +211,10 @@ internal class ModuleInfo
 
 	private void RegisterMethods(object? instance)
 	{
-		foreach (var method in Type.GetMethods()) {
+		foreach (var method in Type.GetMethods(
+			BindingFlags.Public | BindingFlags.NonPublic |
+			BindingFlags.Static | BindingFlags.Instance
+		)) {
 			if (method.Has<SystemAttribute>())
 				Universe.RegisterSystem(instance, method).ChildOf(Entity);
 			if (method.Has<ObserverAttribute>())