feat: adding syncList methods to set an index as dirty

when using classes with synclist there is no way to detect if a class is changed. and setting the index to be the same item again requires first setting it to null.

the new function allows us to use it instead of having to find the index, set null, then set value again.

Assets/Mirage/Runtime/Collections/SyncList.cs

@@ -430,6 +430,38 @@ public int RemoveAll(Predicate<T> match)
             }
         }
 
+        /// <summary>
+        /// Can be used to set item dirty manually.
+        /// <para>should be used with classes to avoid having to clear field first</para>
+        /// <para>Will invoke OnSet</para>
+        /// </summary>
+        /// <param name="item"></param>
+        /// <exception cref="ArgumentException">Throws when item is not found in this synclist</exception>"
+        public void SetItemDirty(T item)
+        {
+            var index = IndexOf(item);
+            if (index >= 0)
+            {
+                SetItemDirtyAt(index);
+            }
+            else
+            {
+                throw new ArgumentException("Item could not be found in list");
+            }
+        }
+
+        /// <summary>
+        /// Can be used to set item dirty manually.
+        /// <para>should be used with classes to avoid having to clear field first</para>
+        /// </summary>
+        /// <param name="item"></param>
+        public void SetItemDirtyAt(int index)
+        {
+            // need to also call OnSet, so that it matches what happens on client side. See other uses of Op_Set
+            OnSet?.Invoke(index, _objects[index], _objects[index]);
+            AddOperation(Operation.OP_SET, index, _objects[index]);
+        }
+
         public Enumerator GetEnumerator() => new Enumerator(this);
 
         IEnumerator<T> IEnumerable<T>.GetEnumerator() => new Enumerator(this);