Add rnback website to showcase (docsifyjs#287)

Author: maximRnback

README.md

@@ -83,6 +83,7 @@ These projects are using docsify to generate their sites. Pull requests welcome
 | [xTeko](https://docs.xteko.com/) | Addins framework for Pin 3.0 |
 | [vue2-datatable-component](https://github.com/OneWayTech/vue2-datatable) | The best Datatable for Vue.js 2.x which never sucks |
 | [Solidarity](https://infinitered.github.io/solidarity/) | Environment enforcer for your projects across machines. |
+| [rnback](https://rnback.com/) | Backend service for react-native applications. |
 
 ## Similar projects