refactor: standardized files name (#1884)

style-guide: https://panjiachen.github.io/vue-element-admin-site/guide/advanced/style-guide.html#style-guide

src/components/MarkdownEditor/index.vue

@@ -9,7 +9,7 @@ import 'tui-editor/dist/tui-editor.css' // editor ui
 import 'tui-editor/dist/tui-editor-contents.css' // editor content
 
 import Editor from 'tui-editor'
-import defaultOptions from './defaultOptions'
+import defaultOptions from './default-options'
 
 export default {
   name: 'MarddownEditor',