:sparkles: 新功能

• 重构懒加载代码，并新增配置项：

lazyload:
# 触发加载的偏移倍数
+ offset_factor: 2
# 指定加载时的占位图片
+ loading_img: /img/loading.gif

• FrontMatter 可以设置 keywords 参数：

---
title: 文章标题
keywords: [关键词1, 关键词2]
---

• 增加分类文章排序字段：

category:
+ post_order_by: "-date"

• 根据 Waline 官方新增配置项：

waline:
+ avatarCDN:
+ anonymous:

• 根据 Twikoo 官方新增配置项：

twikoo:
- env_id:
+ envId:
+ region: ap-shanghai
+ path: window.location.pathname

:bug: 修复

• 修复部分图片样式异常，如关于页的悬浮二维码
• 修复分类没有同时显示文章与子分类
• 修复懒加载在 PWA 中报错以及在友链页未生效
• 修复分类锚点每次生成会变更的问题

:sparkles: Feature

• Refactor Lazyload code and add new config items:

lazyload:
# The factor of viewport height that triggers loading
+ offset_factor: 2
# The placeholder image when loading
+ loading_img: /img/loading.gif

• keywords can be set in FrontMatter:

---
title: The introduction of Fluid
keywords: [hexo, theme, blog]
---

• Config of the category page added new item:

category:
+ post_order_by: "-date"

• Config of Waline added new items:

waline:
+ avatarCDN:
+ anonymous:

:bug: Fix

• Fix some images anomalies, such as QR code on the about page
• Fix that category doesn't contain both posts and subcategories
• Fix lazyload doesn't work in some cases
• Fix an issue where the category anchor would change each time it was generated