feat: Find & FindRequired for general type search

Engine.Core/Exceptions/NotFoundException.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Syntriax.Engine.Core.Exceptions;
+
+public class NotFoundException(string? message) : Exception(message)
+{
+    public static NotAssignedException FromType<T>()
+        => new($"{typeof(T).FullName} was not found");
+}