update readme for new swift/xcode requirements

Author: klundberg

README.md

@@ -10,8 +10,8 @@ CombineCoreBluetooth is a library that bridges Apple's `CoreBluetooth` framework
 ## Requirements:
 
 - iOS 13, tvOS 13, macOS 10.15, or watchOS 6
-- Xcode 12 or higher
-- Swift 5.3 or higher
+- Xcode 13.3 or higher
+- Swift 5.6 or higher
 
 ## Installation