Update README.md

Author: mbrandonw

README.md

@@ -1,6 +1,7 @@
 # 📸 SnapshotTesting
 
 [![CI](https://github.com/pointfreeco/swift-snapshot-testing/workflows/CI/badge.svg)](https://actions-badge.atrox.dev/pointfreeco/swift-snapshot-testing/goto)
+[![Slack](https://img.shields.io/badge/slack-chat-informational.svg?label=Slack&logo=slack)](http://pointfree.co/slack-invite)
 [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fpointfreeco%2Fswift-snapshot-testing%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/pointfreeco/swift-snapshot-testing)
 [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fpointfreeco%2Fswift-snapshot-testing%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/pointfreeco/swift-snapshot-testing)