📝 update change detection docs

Author: krispya

README.md

@@ -364,6 +364,26 @@ world
   .updateEach(([position, velocity]) => {}, { changeDetection: 'always' })
 ```
 
+Changed detection shallowly compares the scalar values with, just like React. This means objects and arrays will only be detected as changed if a new array or object is committed to the store. While immutable state is a great design pattern, it creates memory pressure and reduces performance so instead you can mutate and manually flag a changed has occured.
+
+```js
+// ❌ This change will not be detected since the array is mutated and will pass the comparison
+world.query(Inventory).updateEach(([inventory]) => {
+  inventory.items.push(item)
+})
+
+// ✅ This change will be detected since a new array is created and the comparison will fail
+world.query(Inventory).updateEach(([inventory]) => {
+  inventory.items = [...inventory.items, item]
+})
+
+// ✅ This change is manually flagged and we still get to mutate for performance
+world.query(Inventory).updateEach(([inventory], entity) => {
+  inventory.items.push(item)
+  entity.changed()
+})
+```
+
 ### World traits
 
 For global data like time, these can be traits added to the world. **World traits do not appear in queries.**