[ECO-5624] Added README section for unity usage

Author: sacOO7

README.md

@@ -100,6 +100,11 @@ channel.Subscribe(message =>
 await channel.PublishAsync("test-event", "Hello World!");
 ```
 
+### Unity usage
+
+- Download latest `ably.io.*.unitypackage` from [releases section](https://github.com/ably/ably-dotnet/releases) and include it in the project.
+- Check out the [Unity demo Dashboard app](./unity/Assets/Ably/Examples/Dashboard/) for a complete Ably SDK setup, showcasing channel usage, presence, and pub-sub functionality all integrated with a console view.
+
 ## Releases
 
 The [CHANGELOG.md](./CHANGELOG.md) contains details of the latest releases for this SDK. You can also view all Ably releases on [changelog.ably.com](https://changelog.ably.com).