Update README.md to add shield badges (#5)

* Update README.md

Add shields.io badges for swift version and platform compatibility

* Use compatibility badges from the Swift Package Index Page

README.md

@@ -1,4 +1,5 @@
 ![Y—Analytics Adobe](https://user-images.githubusercontent.com/1037520/231185335-807d15b5-fa0b-4dd5-aba4-b7be18001d95.jpeg)
+[![Swift](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fyml-org%2Fyanalytics-adobe-ios%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/yml-org/yanalytics-adobe-ios) [![Platforms](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fyml-org%2Fyanalytics-adobe-ios%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/yml-org/yanalytics-adobe-ios)  
 _An Adobe implementation of Y—Analytics' `AnalyticsEngine` protocol._
 
 This framework links the [Adobe Experience Platform Analytics SDK](https://github.com/adobe/aepsdk-analytics-ios) to implement an Adobe version of [Y—Analytics](https://github.com/yml-org/yanalytics-ios)' `AnalyticsEngine` protocol.