docs: Adds SPI badges

Author: NeedleInAJayStack

README.md

@@ -1,5 +1,8 @@
 # Swift Haystack
 
+[![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FNeedleInAJayStack%2Fswift-haystack%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/NeedleInAJayStack/swift-haystack)
+[![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FNeedleInAJayStack%2Fswift-haystack%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/NeedleInAJayStack/swift-haystack)
+
 An implementation of [Project Haystack](https://project-haystack.org/) in Swift.
 
 ## Getting Started