Add license mention

README.md

@@ -2,6 +2,7 @@
 
 [![crates.io](https://img.shields.io/crates/v/bevy_replicon_renet)](https://crates.io/crates/bevy_replicon_renet)
 [![docs.rs](https://docs.rs/bevy_replicon_renet/badge.svg)](https://docs.rs/bevy_replicon_renet)
+[![license](https://img.shields.io/crates/l/bevy_replicon_renet)](#license)
 [![codecov](https://codecov.io/gh/projectharmonia/bevy_replicon_renet/graph/badge.svg?token=ZrlFB8wBpO)](https://codecov.io/gh/projectharmonia/bevy_replicon_renet)
 
 An integration of [`bevy_renet`](https://github.com/lucaspoffo/renet/tree/master/bevy_renet) as a messaging backend for [`bevy_replicon`](https://github.com/projectharmonia/bevy_replicon).
@@ -22,3 +23,7 @@ See also [examples](examples).
 | 0.0.11     | 0.26          | 0.3                 |
 | 0.0.11     | 0.25          | 0.2                 |
 | 0.0.11     | 0.24          | 0.1                 |
+
+## License
+
+Licensed under either of [Apache License, Version 2.0](LICENSE-APACHE) or [MIT License](LICENSE-MIT) at your option.