[MINOR] Add compatibility badges

### What changes were proposed in this pull request?

This PR aims to add `Compatibility` badges to the README.md file.

### Why are the changes needed?

It will show the info like the following.

<img width="718" alt="Screenshot 2025-03-12 at 09 48 16" src="https://github.com/user-attachments/assets/cec8d412-fb3e-47b0-93bb-8ad59dab8c0c" />

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Manual review.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #12 from dongjoon-hyun/minor.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

README.md

@@ -1,6 +1,8 @@
 # Apache Spark Connect Client for Swift
 
 [![GitHub Actions Build](https://github.com/apache/spark-connect-swift/actions/workflows/build_and_test.yml/badge.svg)](https://github.com/apache/spark-connect-swift/blob/main/.github/workflows/build_and_test.yml)
+[![Swift Version Compatibility](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fapache%2Fspark-connect-swift%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/apache/spark-connect-swift)
+[![Platform Compatibility](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fapache%2Fspark-connect-swift%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/apache/spark-connect-swift)
 
 This is an experimental Swift library to show how to connect to a remote Apache Spark Connect Server and run SQL statements to manipulate remote data.