add license badge

Author: newpavlov

README.md

@@ -1,6 +1,6 @@
 # RustCrypto: Message Authentication Codes
 
-[![Project Chat][chat-image]][chat-link] [![dependency status][deps-image]][deps-link]
+[![Project Chat][chat-image]][chat-link] ![Apache2/MIT licensed][license-image] [![dependency status][deps-image]][deps-link]
 
 Collection of [Message Authentication Code][1] (MAC) algorithms written in pure Rust.
 
@@ -34,6 +34,7 @@ Unless you explicitly state otherwise, any contribution intentionally submitted
 
 [chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
 [chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260044-MACs
+[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
 [deps-image]: https://deps.rs/repo/github/RustCrypto/MACs/status.svg
 [deps-link]: https://deps.rs/repo/github/RustCrypto/MACs
 [msrv-1.41]: https://img.shields.io/badge/rustc-1.41.0+-blue.svg