docs: update Nuxt 3 installation guide (#865)

Author: DamianGlowala

packages/docs/src/guide/installation.md

@@ -150,7 +150,7 @@ import 'floating-vue/dist/style.css'
 <code-group>
 <code-block title="npm">
 ```shell
-npm i -S floating-vue
+npm i floating-vue
 ```
 </code-block>
 
@@ -161,14 +161,12 @@ yarn add floating-vue
 </code-block>
 </code-group>
 
-Add the `floating-vue/nuxt` module to your Nuxt config file:
+Add the `floating-vue/nuxt` module to your `nuxt.config` file:
 
 ```js
-import { defineNuxtConfig } from 'nuxt3'
-
 export default defineNuxtConfig({
-  buildModules: [
-    'floating-vue/nuxt',
-  ],
+  modules: [
+    'floating-vue/nuxt'
+  ]
 })
 ```