chore: update README.md (#592) [ci skip]

packages/reactivity/README.md

@@ -16,4 +16,4 @@ The implementation of this module is inspired by the following prior art in the
 
 ## Caveats
 
-- Built-in objects are not observed except for `Map`, `WeakMap`, `Set` and `WeakSet`.
+- Built-in objects are not observed except for `Array`, `Map`, `WeakMap`, `Set` and `WeakSet`.