docs: add _redirects icon

Author: yuyinws

packages/docs/guide/essentials/history-mode.md

@@ -185,7 +185,7 @@ Add this to your `firebase.json`:
 
 Create a `_redirects` file that is included with your deployed files:
 
-```
+``` [_redirects ~vscode-icons:file-type-light-netlify~]
 /* /index.html 200
 ```
 

packages/docs/zh/guide/essentials/history-mode.md

@@ -184,7 +184,7 @@ rewrite {
 
 创建一个 `_redirects` 文件，包含在你的部署文件中：
 
-```
+``` [_redirects ~vscode-icons:file-type-light-netlify~]
 /* /index.html 200
 ```