docs: add vuepress-theme-reco to README.md

Author: billyyyyy3320

README.md

@@ -43,6 +43,7 @@ Please head [documentation](https://vuepress-theme-blog.ulivz.com/) to see all a
 - [70-lines-of-vuepress-blog-theme](https://github.com/ulivz/70-lines-of-vuepress-blog-theme): A VuePress Blog Theme implemented in around 70 lines.
 - [@vuepress/theme-blog](https://github.com/ulivz/vuepress-theme-blog): Default blog theme for VuePress.
 - [vuepress-theme-modern-blog](https://github.com/z3by/vuepress-theme-modern-blog): A modern theme for Vue press using [Element.UI design system](https://element.eleme.io/#/)
+- [vuepress-theme-reco](https://github.com/vuepress-reco/vuepress-theme-reco) - A simple and beautiful vuepress blog theme
 
 Feel free to add yours here...