Update README.md

Author: SkrewEverything

README.md

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 # macOS Keylogger
 
-[![Swift 3.0](https://img.shields.io/badge/Swift-3.0-orange.svg)]()
+[![Swift 4.0](https://img.shields.io/badge/Swift-4.0-orange.svg)]()
 
 It is a simple and easy to use keylogger for macOS. It is not meant to be malicious. There are only few keyloggers available for mac and none of them are in swift.