feat: Add file names to snippets

contents/pagination.mdx

@@ -9,7 +9,7 @@ title: Pagination
 
 ## HTML
 
-```html
+```html index.html
 <div class="pagination">
     <!-- Pagination item -->
     <div class="pagination__item">...</div>
@@ -21,7 +21,7 @@ title: Pagination
 
 ## CSS
 
-```css
+```css styles.css
 .pagination {
     display: flex;