Add jekyll-themes.com badge.

Author: sighingnow

README.md

@@ -4,7 +4,9 @@ Make Jelly site have a GitBook look!
 
 ## Demo
 
-[https://sighingnow.github.io/jekyll-gitbook](https://sighingnow.github.io/jekyll-gitbook)
+Live demo on Github Pages: [https://sighingnow.github.io/jekyll-gitbook](https://sighingnow.github.io/jekyll-gitbook)
+
+[![Jekyll Themes](https://img.shields.io/badge/featured%20on-JekyllThemes-red.svg)](https://jekyll-themes.com/jekyll-gitbook/)
 
 ## Why Jekyll with GitBook
 
@@ -33,4 +35,4 @@ Copyright 2019 Tao He.
 
 [1]: https://pages.github.com
 [2]: https://pages.github.com/themes
-[3]: https://github.com/sighingnow/jekyll-gitbook/fork
+[3]: https://github.com/sighingnow/jekyll-gitbook/fork