feat: add configs introduced in Hexo v4
feat: add configs introduced in Hexo v4

- pretty_urls.trailing_index: https://github.com/hexojs/hexo/pull/3691
- external_link.enable: https://github.com/hexojs/hexo/pull/3675
- meta_generator: https://github.com/hexojs/hexo/pull/3653
- use_date_for_updated: https://github.com/hexojs/hexo/pull/3235

linzb93/blog,linzb93/blog