move puzzle implementations out of engine

Assets/Engine/Runtime/Modules/State/Spawn.cs

@@ -0,0 +1,13 @@
+namespace EscapeRoomEngine.Engine.Runtime.Modules.State
+{
+    /// <summary>
+    /// The spawn door is used in the first room.
+    /// </summary>
+    internal class Spawn : DoorState
+    {
+        private void Start()
+        {
+            ExitFrom();
+        }
+    }
+}