docs: wip

Author: posva

docs/cookbook/migration-v2-v3.md

@@ -15,7 +15,13 @@ VueFire 3 introduces a Composition API that is more flexible and powerful than t
 
 ### Removal of `serialize` option for Firestore
 
-Firestore support a native equivalent of the `serialize` option: [Firestore Data Converter](https://firebase.google.com/docs/firestore/query-data/get-data#custom_objects). You can use it to convert your data to a class instance. This is the recommended way to use Firestore with VueFire **and make it typesafe**.
+Firestore supports a native equivalent of the `serialize` option: [Firestore Data Converter](https://firebase.google.com/docs/firestore/query-data/get-data#custom_objects). You can use it to convert your data to a class instance. This is the recommended way to use Firestore with VueFire **and make it typesafe**.
+
+VueFire does support a **global `converter` option** that is equivalent to the previous global `serialize` option. Note that, like the its predecessor `serialize`, VueFire uses a default converter that adds the `id` property to your data, you can import it to use it:
+
+```ts
+// TODO:
+```
 
 ## Vuexfire