Add AacFlLayer.WithDefaultState(...) to change the default state:

- Add WithDefaultState to change the default state of a layer

Framework/Editor/V0/Aac.cs

@@ -239,6 +239,12 @@ namespace AnimatorAsCode.V0
 
             WithAvatarMask(avatarMask);
         }
+
+        public AacFlLayer WithDefaultState(AacFlState newDefaultState)
+        {
+            _stateMachine.WithDefaultState(newDefaultState);
+            return this;
+        }
     }
 
     public class AacFlBase

Framework/Editor/V0/AacFlStates.cs

@@ -197,6 +197,12 @@ namespace AnimatorAsCode.V0
         {
             return new Vector3(x * _gridShiftX , y * _gridShiftY, 0);
         }
+
+        public AacStateMachine WithDefaultState(AacFlState newDefaultState)
+        {
+            _machine.defaultState = newDefaultState.State;
+            return this;
+        }
     }
 
     public class AacFlState