docs: some updates

Author: posva

docs/cookbook/migration-v2-v3.md

@@ -1,8 +1,28 @@
 # Upgrading to VueFire v3
 
-VueFire v2 and VueFire v3 have a lot in common but a big improvement to the Vue.js Ecosystem happened between them: the Composition API. On top of that, Firebase SDK itself evolved a lot. VueFire v3 is built on top of the Composition API to provide an idiomatic way to use Firebase with Vue.js that works with **both Vue 2 and Vue 3**. This means that if you are still on Vue 2, as long as you are **using Vue 2.7**, you can upgrade to VueFire v3 and use the Composition API or the Options API. It also relies on the new Firebase SDK v9 which provides a modular API that greatly improves the final size of your application. Therefore, these are the requirements to upgrade to VueFire v3:
+VueFire v2 and VueFire v3 have a lot in common but a big improvement to the Vue.js Ecosystem happened between them: the Composition API. On top of that, Firebase SDK itself evolved a lot. VueFire v3 is built on top of the Composition API to provide an idiomatic way to use Firebase with Vue.js that works with **both Vue 2 and Vue 3**. This means that if you are still on Vue 2, as long as you are **using Vue 2.7**, you can upgrade to VueFire v3 and use the Composition API or the Options API. It also relies on the new Firebase SDK v9 which provides a modular API that greatly improves the final size of your application.
+
+Therefore, these are the requirements to upgrade to VueFire v3:
 
 - Use Vue 2.7 or higher
 - Use Firebase SDK v9 or higher
 
+## General recommendations
+
+VueFire 3 introduces a Composition API that is more flexible and powerful than the Options API. It keeps the existing Options API as a wrapper around the Composition API but we recommend you to give the Composition API a try as it gives you more control over your data state.
+
+## Breaking changes
+
+### 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**.
+
 ## Vuexfire
+
+:::tip
+If you are using [Pinia](https://pinia.vuejs.org/), make sure to check the [Pinia guide](./subscriptions-external.md#pinia) instead.
+:::
+
+As of VueFire 3, Vuexfire doesn't have an exact replacement. This is because the Composition API allows us to have the same functionality without the need for a plugin.
+
+TODO: example

docs/guide/getting-started.md

@@ -14,7 +14,7 @@ npm install vuefire@next firebase
 
 :::warning
 
-- VueFire requires Firebase JS SDK >= 9 but **is compatible with Vue 2 and Vue 3**. It's currently in alpha, make sure to check [the Roadmap](https://github.com/vuejs/vuefire/issues/1241) and report any issue you find.
+VueFire requires Firebase JS SDK >= 9 but **is compatible with Vue 2 and Vue 3**. It's currently in alpha, make sure to check [the Roadmap](https://github.com/vuejs/vuefire/issues/1241) and report any issue you find.
 
 :::