修复bug，新增特性。
What's Changed
- bug:搜索 by @tangly1024 in #140
- Preview by @tangly1024 in #141
- hexo: 文章页默认背景图 by @tangly1024 in #142
- Feature og url image, path env fix for vercel deploy by @txs in #146
- Better SEO for Facebook Open Graph by @txs in #152
- Feature last update time by @tangly1024 in #155
- bug-滚动到评论区 by @tangly1024 in #156
- Add Facebook Customer Chat for the blogging system by @txs in #153
- Feature facebook messenger customer chat plugin no ssr by @txs in #154
Full Changelog: v2.9.1...v3.0.0