docs: update docs

Author: hunterliu1003

docs/content/2.get-started/1.guide/2.setup.md

@@ -22,6 +22,8 @@ How to start with Vue Final Modal, by creating a fresh new project or adding it
 
 ## Plugin registration
 
+In vue-final-modal 4, it's necessary to create a plugin by `createVfm()`{lang=ts} and register it because vue-final-modal 4 has some shared context that is based on provide/inject.
+
 ### Vue 3
 
 ```ts [main.ts]
@@ -49,6 +51,8 @@ export default defineNuxtPlugin((nuxtApp) => {
 
 ## Import required CSS
 
+vue-final-modal 4 has tiny size of required CSS (gzipped 0.49kb). All classes have a `.vfm-` prefix, so you don't have to worry about any CSS pollution. _[See style of `<VueFinalModal>`.](https://github.com/vue-final/vue-final-modal/blob/v4/packages/vue-final-modal/src/components/CoreModal/CoreModal.vue#L184-L217)_
+
 ### Vue 3
 
 ```ts [main.ts]
@@ -64,6 +68,43 @@ export default defineNuxtConfig({
 
 ```
 
+## Add `<ModalsContainer>` to Vue tree
+
+`<ModalsContainer>` is a container for the dynamic modals that created by `useModal()`.
+
+You don't need to do add anything else to the `<ModalsContainer>`{lang=ts}, as long as you include it in your Vue tree, you can use Dynamic modals.
+
+### Vue 3
+
+```vue [App.vue]
+<script setup lang="ts">
+import { ModalsContainer } from 'vue-final-modal'
+</script>
+
+<template>
+  <div>
+    ...
+    <ModalsContainer />
+  </div>
+</template>
+```
+
+### Nuxt 3
+
+```vue [layouts/default.vue]
+<script setup lang="ts">
+import { ModalsContainer } from 'vue-final-modal'
+</script>
+
+<template>
+  <div>
+    Some default layout shared across all pages
+    <slot />
+    <ModalsContainer />
+  </div>
+</template>
+```
+
 ## Style a modal
 
 Define a styled modal for yourself. Here will create a styled `<ConfirmModal>`{lang=ts} with `<VueFinalModal>`{lang=ts} as an example.