docs: fix typo (#225)

docs/content/en/usage/sitemap.md

@@ -9,7 +9,7 @@ category: Usage
 
 By default, the sitemap is setup to the following path: `/sitemap.xml`  
 
-All static routes (eg. `/pages/about.vue`) are automatically add to the sitemap, but you can exclude each of them with the [`exclude`](/usage/sitemap-options#exclude-optional---string-array) property.  
+All static routes (eg. `/pages/about.vue`) are automatically added to the sitemap, but you can exclude each of them with the [`exclude`](/usage/sitemap-options#exclude-optional---string-array) property.  
 
 For dynamic routes (eg. `/pages/_id.vue`), you have to declare them with the [`routes`](/usage/sitemap-options#routes-optional---array--function) property. This option can be an array or a function. In addition, the routes defined in `generate.routes` will be automatically used for the sitemap.