docs: correct spelling in alert tutorial from 'Ussage' to 'Usage'

Author: SerVitasik

adminforth/documentation/docs/tutorial/03-Customization/07-alert.md

@@ -34,7 +34,7 @@ import adminforth from '@/adminforth';
 const isConfirmed = await adminforth.confirm({message: 'Are you sure?', yes: 'Yes', no: 'No'})
 ```
 
-## Ussage example
+## Usage example
 
 Create a Vue component in the custom directory of your project, e.g. `Alerts.vue`: