Update frontend.md
Update frontend.md

laravel 5.5.0 Vue example component 为 Example.vue 但是在 laravel 5.5.22中为ExampleComponent.vue

laravel 5.5 英文文档中为ExampleComponent.vue 
https://laravel.com/docs/5.5/frontend#writing-javascript
iwzh/laravel-docs,khs1994-gitbook/laravel-docs,laravel-china/laravel-docs