Update README.md (#1169)

README.md

@@ -1,7 +1,7 @@
-> **Warning**
+> [!Warning]
 > This project is in early development, it does however work with real sats! Always use amounts you don't mind losing.
 
-[![crates.io](https://img.shields.io/crates/v/cdk.svg)](https://crates.io/crates/cdk) [![Documentation](https://docs.rs/cdk/badge.svg)](https://docs.rs/cdk)
+[![crates.io](https://img.shields.io/crates/v/cdk.svg)](https://crates.io/crates/cdk) [![Documentation](https://docs.rs/cdk/badge.svg)](https://docs.rs/cdk) [![License](https://img.shields.io/github/license/cashubtc/cdk)](https://github.com/cashubtc/cdk/blob/main/LICENSE)
 
 # Cashu Development Kit