Update index.md

Author: arcxingye

index.md

@@ -5,6 +5,7 @@ Welcome
 *   [网页聊天室](https://arcxingye.github.io/utu.html?url=https://chat.getloli.com/room/@xingye)
 *   [在线黄油列表](https://arcxingye.github.io/game)
 *   [rickroll二维码获取](https://arcxingye.github.io/rr/qrcode)
+*   [r18](https://bonepa.com/9285d94ecb/7c4a4cb298/?placementName=github)
 
 相关主页
 *   [Github](https://github.com/arcxingye)