Update README.md

Author: jeantimex

README.md

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 # How to Implement Collapsible Table Section in iOS
 A simple iOS swift project demonstrates how to implement collapsible table section.
 
+[![Language](https://img.shields.io/badge/Swift-2.2-orange.svg?style=flat)]()
+
 ### Demo ###
 ![demo](screenshots/demo.gif)<br />