Fixed Swift tools version in readme

Author: chiragramani

README.md

@@ -16,7 +16,7 @@ Its API is designed for performance critical applications. It uses value types a
 Add this repository to the `Package.swift` manifest of your project:
 
 ```swift
-// swift-tools-version:4.2
+// swift-tools-version:5.2
 import PackageDescription
 
 let package = Package(