feat: enhance Waline comment configuration with avatar options

- Added avatar settings including 'avatar', 'avatarCDN', and 'avatarForce' to the Waline comment configuration in waline.html.
- Updated placeholder text for the comment input field to maintain consistency.

_includes/comments/waline.html

@@ -11,7 +11,10 @@
         login: 'disable',
         requiredMeta: ['nick', 'mail'],
         meta: ['nick', 'mail', 'link'],
-        placeholder: '欢迎评论！昵称和邮箱为必填项~'
+        placeholder: '欢迎评论！昵称和邮箱为必填项~',
+        avatar: 'retro',
+        avatarCDN: 'https://seccdn.libravatar.org/avatar/',
+        avatarForce: false
     });
 </script>
 <link rel="stylesheet" href="https://unpkg.com/@waline/client@v2/dist/waline.css" />